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lm1270 hi-brite 200 mhz i 2 c compatible rgb image enhancer with video auto sizing general description the lm1270 is a supplementary ic to the low cost chipset (lccs). it modifies the video stream prior to the lccs preamplifier. the key function of the lm1270 is image pro- cessing for enhancing pictures or motion video. image en- hancement is accomplished by special intermediate fre- quency boosting. 200 mhz bandwidth assures minimal impact on the video change when adding the lm1270. other functions of the lm1270 are: 1. measures the length of the active video and its front porch time with respect to the horizontal flyback and vertical sync for auto alignment information. 2. calibration mode for determining the start of the image coordinates. 3. data receiver for receiving data encoded on video. 4. window highlight with respect to the horizontal and ver- tical sync, used with the image enhancing feature. 5. video source selection, allowing the choice of two ana- log inputs. features n ideal companion ic to the lccs to provide image enhancing for viewing pictures or motion video n programmable clamp generator n programmable blank generator n video detection controlled by i 2 c compatible bus, allowing easy and accurate hi-brite window calibration n programmable window hi-brite function n programmable image sharpness control (tv emphasis), adjustable for different line rates n measures video position with respect to the horizontal flyback and vertical sync pulses, providing necessary information for auto-sizing n emphasis done either inside or outside the window applications n any monitor designed with the lccs chip set n standard 0.7v video output assures compatibility with any video pre-amp block and connection diagram 20063501 figure 1. order number LM1270N see ns package number n24d may 2003 lm1270 hi-brite 200 mhz i 2 c compatible rgb image enhancer with video auto sizing ? 2003 national semiconductor corporation ds200635 www.national.com
absolute maximum ratings (notes 1, 3) if military/aerospace specified devices are required, please contact the national semiconductor sales office/ distributors for availability and specifications. supply voltage, pins 9 and 18 6.0v peak video output source current (any one amp) pins 19, 20 or 21 28 ma voltage at any input pin (v in )v cc +0.5 > v in > ?0.5v power dissipation (p d ) (above 25?c derate based on ja and t j ) 2.4w thermal resistance to ambient ( ja ) 51?c/w thermal resistance to case ( jc ) 32?c/w junction temperature (t j ) 150?c esd susceptibility (note 4) 2 kv esd machine model (note 5) 200v storage temperature ?65?c to +150?c lead temperature (soldering, 10 sec.) 265?c operating ratings (note 2) temperature range 0?c to +70?c supply voltage (v cc & pll v cc ) 4.75v < v cc < 5.25v video inputs 0.0v < v in < 1.0v p-p active video signal electrical characteristics unless otherwise noted: t a = 25?c, v cc = +5v, v in = 0.7v, c l = 5 pf, video signal output = 0.7v p-p . symbol parameter conditions min (note 7) typ (note 6) max (note 7) units i cc maximum supply current both supplies, r l = (note 8) 165 235 ma i cc-ps maximum supply current, power save mode both supplies, r l = (note 8) 15 25 35 ma le linearity error triangular signal input source (note 9) 5% v o blk typ typical video black level output test setting 4, no ac input signal 1.2 1.4 1.6 vdc v o blk a-b typical video black level difference a-b no ac input signal ?0.05 0 0.05 vdc v o white-max white level video output voltage video in = 0.7v 0.9 1.0 1.1 v t r rise time 10% to 90%, ac input signal (note 10) 1.9 ns os r overshoot (rising edge) ac input signal (note 10) 6 % t f fall time 90% to 10%, ac input signal (note 10) 2.0 ns os f overshoot (falling edge) ac input signal (note 10) 8 % f (?3 db) video amplifier bandwidth (note 12) v o =1v p-p 200 mhz v sep 10 khz video amplifier 10 khz isolation (note 14) ?70 db v sep 10 mhz video amplifier 10 mhz isolation (note 14) ?50 db a v max maximum voltage gain reg. 09 & 0a = 7fh, ac input signal 1.3 1.4 1.5 v/v a v 1/2 contrast @ 50% level reg. 09 & 0a = 40h, ac input signal ?5 db a v min maximum contrast attenuation reg. 09 & 0a = 00h, ac input signal ?10 db a v match absolute gain match @ a v max reg. 09 & 0a = 7fh, ac input signal 0.5 db a v track gain change between amplifiers tracking when changing a v max to a v 1/2 (note 11) 0.5 db vid threshold video threshold normal operation 80 mv v clamp max clamp gate low input voltage default mode, clamp comparators off 2.2 v v clamp min clamp gate high input voltage default mode, clamp comparators on 2.8 v i clamp low clamp gate input current default mode, v 24 = 0v ?1.6 ?1.4 ?1.1 ma lm1270 www.national.com 2
active video signal electrical characteristics (continued) unless otherwise noted: t a = 25?c, v cc = +5v, v in = 0.7v, c l = 5 pf, video signal output = 0.7v p-p . symbol parameter conditions min (note 7) typ (note 6) max (note 7) units i clamp high clamp gate input current default mode, v 24 = 4v 0.5 0.7 0.9 ma t pw clamp back porch clamp pulse width default mode (note 15) 200 ns t clamp-video end of clamp pulse to start of active video default mode, limit is guaranteed by design 50 ns v clamp high out clamp gate high output voltage internal clamp is output at pin 24 3.2 v i clamp high out clamp gate high output current internal clamp is output at pin 24 10 a v clamp low out clamp gate low output voltage internal clamp is output at pin 24 0.4 v i clamp low out clamp gate low output current internal clamp is output at pin 24 ?10 a r in-video input resistance 20 m ? v ref r ext v ref r ext output voltage 10 k ? , 1% resistor; pin 23 to gnd 1.26 1.44 1.64 v v spot spot killer voltage v cc adjusted to activate 3.40 4.0 4.25 v external interface signals electrical characteristics unless otherwise noted: t a = 25?c, v cc = +5v, v in = 0.7v, c l = 5 pf, video output = 0.7 v p-p . symbol parameter conditions min (note 7) typ (note 6) max (note 7) units v l (i 2 c) i 2 c compatible low input voltage sda or scl inputs ?0.5 1.5 v v h (i 2 c) i 2 c compatible high input voltage sda or scl inputs 3.0 v cc + 0.5 v i l (i 2 c) i 2 c compatible low input current sda or scl, input voltage = 0.4v 10 a i h (i 2 c) i 2 c compatible high input current sda or scl, input voltage = 4.5v 10 a v ol (i 2 c) i 2 c compatible low output voltage i o = 3 ma 0.5 v i in threshold i in h-flyback detection threshold ?35 a i in-operating minimum ? insure normal operation lowest operating horizontal frequency in given application (note 15) ?50 a maximum ? should not exceed in normal operation ?550 i in flyback peak current during flyback period, recommended design range operating range for all horizontal scan frequencies, maximum current should not exceed 4 ma (note 15) 2.0 3.0 4.0 ma note 1: limits of absolute maximum ratings indicate limits below which damage to the device must not occur. note 2: limits of operating ratings indicate required boundaries of conditions for which the device is functional, but may not meet specific performance lim its. note 3: all voltages are measured with respect to gnd, unless otherwise specified. note 4: human body model, 100 pf capacitor discharged through a 1.5 k ? resistor. note 5: machine model esd test is covered by specification eiaj ic-121-1981. a 200 pf capacitor is charged to the specified voltage, then discharged directly into the ic with no external series resistor (resistance of discharge path must be under 50 ? ). note 6: typical specifications are specified at +25?c and represent the most likely parametric norm. note 7: tested limits are guaranteed to national?s aoql (average outgoing quality level). note 8: the supply current specified is the quiescent current for v cc with r l = . load resistors are not required and are not used in the test circuit, therefore all the supply current is used by the pre-amp. note 9: linearity error is the variation in step height of a 16 step staircase input signal waveform with a 0.7 v p-p level at the input, subdivided into 16 equal steps, with each step approximately 100 ns in width. note 10: input from signal generator: t r ,t f < 1 ns. scope and generator response used for testing: t r = 1.1 ns, t f = 0.9 ns. using the rss technique the scope and generator response have been removed from the output rise and fall times. note 11: ? a v track is a measure of the ability of any two amplifiers to track each other and quantifies the matching of the three gain stages. it is the difference in gain change between any two amplifiers with the contrast set to a v 1/2 and measured relative to the a v max condition. for example, at a v max the three amplifiers? gains might be 0.1 db, ?0.1 db, and ?0.2 db and change to ?5.2 db, ?4.9 db and ?4.7 db respectively for contrast set to a v 1/2 . this yields a typical gain change of ?5.0 db with a tracking change of 0.2 db. note 12: adjust input frequency from 10 mhz (a v max reference level) to the ?3 db corner frequency (f ?3 db ). note 13: measure output levels of the other two undriven amplifiers relative to the driven amplifier to determine channel separation. terminate the undriven amplifier inputs to simulate generator loading. repeat test at f in = 10 mhz for v sep 10 mhz . note 14: a minimum pulse width of 200 ns is guaranteed for a horizontal line of 15 khz. this limit is guaranteed by design. if a lower line rate is used then a longer clamp pulse may be required. lm1270 www.national.com 3
external interface signals electrical characteristics (continued) note 15: limits met by matching the external resistor going to pin 24 to the h flyback voltage. typical performance characteristics v cc = 5v, t a = 25?c unless otherwise specified. emphasis, center frequency at maximum center frequency, emphasis at maximum 20063502 20063503 the above two plots show the processing done by the lm1270 on the video input signal. there are two variables for the video processing, emphasis and center frequency. emphasis is controlled by bits 0-2 in register 0b. this gives 8 different levels of emphasis. in the above plot the center frequency is set at its maximum level and the 8 different levels of emphasis is measured. the output video with no emphasis is adjusted to a 0.7 v p-p level. using maximum emphasis the video is increased to a 0.9 v p-p level at the rising edge of the video. if the falling edge was measured it would show a similar waveform, but going in the negative direction. center frequency is shown in the second plot. control of the center frequency is done with bits 0-3 in register 0c. this gives 16 adjustments for this feature. every other adjustment is shown in the above plot, showing all 16 adjustments would have made the plot too hard to read. the curves closely approximate the peaking of an rc network, therefore the term center frequency means the rc time constant that is approximated by each curve in the above plot. a true rc peaking network would give very large overshoots. the lm1270 has special circuitry to clip the very large over- shoots, yet has the complete benefit of the rc peaking. this special circuitry allows for much more overshoot than one could do with rc peaking and still not saturate the video channel. note that the video channel with the emphasis also has its own independent contrast control. this allows the user to adjust his monitor for a brighter picture within the hi-brite window and optimize the emphasis for the resolution he is using with the monitor. now the user of the monitor can give his pictures or video a special ?sparkle? when using the capabilities of the lm1270. lm1270 www.national.com 4
pin descriptions pin no. pin name schematic description 1 2 3 blue 1 video in red 1 video in green 1 video in channel 1 video inputs. these inputs must be ac coupled with a 0.1 f cap. dc restoration is done at these inputs. a series resistor of about 33 ? and external esd protection diodes should also be used. channel 1 video passes through the emphasis section used for the hi-brite window. when using hi-brite the channel 1 input pin must be shorted to the corresponding channel 2 input pin. 4 analog input ground ground pin for the input analog circuits of the lm1270 5 6 7 blue 2 video in red 2 video in green 2 video in channel 2 video inputs. these video inputs must be ac coupled with a 0.1 f cap. dc restoration is done at these inputs. a series resistor of about 33 ? and external esd protection diodes should also be used. when using hi-brite the channel 2 input pin must be shorted to the corresponding channel 1 input pin. 8 10 digital ground pll v cc the ground pin should be connected to the rest of the circuit ground by a short but independent pcb trace to prevent contamination by extraneous signals. the v cc pin should be isolated from the rest of the v cc line by a ferrite bead and bypassed to pin 8 with an electrolytic capacitor and a high frequency ceramic. 9 pll filter recommended topology and values are shown to the left. it is recommended that both filter branches be bypassed to the independent ground as close to pin 8 as possible. great care should be taken to prevent external signals from coupling into this filter from video, i 2 c compatible bus, etc. 11 v sync logic level vertical sync signal received from the video card in the pc or sync stripper circuit. lm1270 www.national.com 5
pin descriptions (continued) pin no. pin name schematic description 12 h sync logic level horizontal sync signal received from the video card in the pc or sync stripper circuit. 13 scl the i 2 c compatible clock line. a pull-up resistor of about 2 k ? should be connected between this pin and v cc . a 100 ? resistor should be connected in series with the clock line for additional esd protection. 14 sda the i 2 c compatible data line. a pull-up resistor of about 2 k ? should be connected between this pin and v cc . a 100 ? resistor should be connected in series with the data line for additional esd protection. 15 blank/interrupt out this output pin can be selected for vertical blank, blank all the video, or no blanking. provides the blanking signal normally used at g1 of the crt, blanking the video during vertical retrace. if blanking is not required, this pin may be used as an interrupt signal for the microcontroller. 16 h flyback proper operation requires current reversal. r h should be large enough to limit the peak current at pin 16 to about +2 ma during blanking, and ?300 a during scan. c 17 is usually needed for logic level inputs and should be large enough to make the time constant, r h c 17 significantly larger than the horizontal period. r fil and c fil are typically 300 ? and 330 pf when the flyback waveform has ringing and needs filtering. these two parts are not used on the current neck board. c 57 may be needed to filter extraneous noise and can be up to 100 pf. lm1270 www.national.com 6
pin descriptions (continued) pin no. pin name schematic description 17 18 ground v cc ground pin for the output analog portion of the lm1270 circuitry, and power supply pin for all the analog of the lm1270. note the recommended charge storage and high frequency capacitors which should be as close to pins 17 and 18 as possible. 19 20 21 green video out red video out blue video out video outputs of the lm1270. typically the output is set to 0.7 v p-p to drive any standard video pre-amp. when hi-brite is activated the user can set the video output as high as 1.0 v p-p . 22 v ref cap provides filtering for the internal voltage which sets the internal bias current in conjunction with r ext .a minimum of 0.1 f is recommended for proper filtering. this capacitor should be placed as close to pin 22 and the analog ground return as possible. this pin can also be set to use an external v ref . 23 v ref r ext sets the internal current sources through a 10 k ? 1% external resistor. resistor value and accuracy is critical for optimum operation of the lm1270. this resistor should be placed as close to pin 23 and the analog ground return as possible. 24 clamp this pin can either accept an external clamp pulse or send an internally generated clamp pulse to the video circuits. as an input this pin accepts either ttl or cmos logic levels. the internal switching threshold is approximately one-half of v cc .an external series resistor, r clp , of about 1 k ? is recommended to avoid overdriving the input devices, or for current limiting the drivers if being used as an output. c clp may be necessary for filtering noise on the clamp input. r load should be used if this pin is an output with a value of about 10 k ? . lm1270 www.national.com 7
functional description video section the lm1270 gives the monitor designer the ability to add a highlighted window to the crt monitor. special software provided manufacturer enables the user to select the area he wants to have highlighted. national semiconductor refers to this feature as hi-brite. referring to figure 1 , the block diagram of the lm1270, note that there are two channels for each video input. of the three video channels only the blocks of the blue channel are shown since all three channels have the same blocks. a buffer stage is located at the video inputs and this is followed by a contrast control. referring to chan- nel one (b1 input), the contrast control is followed by an emphasis block. the combination of the emphasis control and the contrast control gives the desired highlighted video inside the hi-brite window. the output of the emphasis stage and the output of the contrast control in channel two go to a high-speed video switch, which selects the video channel going to the output stage. having an independent contrast control in each video chan- nel allows the user to adjust the video gain, normally having the higher gain in channel one, giving a ?brighter? picture within the hi-brite window. the emphasis stage is used to give more ?sparkle? to the highlighted video. video going into the emphasis stage has peaking added to the video. both the amplitude and the duration of the peaking are adjustable through the i 2 c compatible bus, optimizing the emphasis for different video resolutions. maximum peaking is 20%. al- though most uses of the hi-brite would be for the video inside the selected window, the reverse may be selected where all the video outside the window is processed through the emphasis stage. please remember that for all video inputs the corresponding channel one input and the channel two input must be shorted together. standard ac coupling such as used with the lm123x or lm124x pre-amps is to be used with the lm1270. i 2 c compatible interface pins 13 and 14 receive signals from an i 2 c compatible bus. the interface section is used to decode the i 2 c compatible signal and update the registers. note that all functions of the lm1270 are controlled through an i 2 corani 2 c compatible bus. details on the internal registers are covered in the i 2 c compatible interface registers section. pll a phase locked loop (pll) is required for the lm1270 to sync all the timing circuits to the incoming horizontal sync. proper operation of both the hi-brite window and the video detec- tion requires a proper lock of the pll reference pulse to the horizontal sync. careful layout of the loop filter at pin 10 is necessary for keeping noise out of the pll section. the register to the pll is used to set the number of pixels per line for the internal counters that set the hi-brite window, gener- ate the internal clamp pulse, and set the counters for the video detection. the maximum number of pixels per line is 2,047, or 7fh. for good resolution of the window, 640 is the recommended minimum pixels per line. the vco has a running frequency range of 110 mhz to 160 mhz when using prescaler 7. for the other pre-scaler settings the frequency range is 120 mhz to 220 mhz. the output of the vco goes to a pre-scaler wit h a 3 bit register, dividing the vco output by up to 8. minimum division is 1, just a straight pass through the pre-scaler. calculating the vco frequency: f vco = vco frequency f h = horizontal line frequency n = number of pixels per line m = pll pre-scaler using the above terms gives the following formula for the pll: f vco =n * m * f h it is easiest to run the pll in auto mode, setting bit 7 of address 0e to a ?1?. here the user programs in the desired pixels per line and the part will select the preferred pre-scaler number. if one is using manual mode below is a table showing the relationship between the pre-scaler and the vco frequency. the chart shows the pixel frequency, f p . f p =f vco /m the necessary pixels per line is calculated by the following formula: n=f p /f h pres c2 pres c2 pres c2 pres div ratio f p (max) mhz f p (min) mhz 1 1 1 1 160.0 110.0 1 1 0 2 110.0 60.0 1 0 1 3 73.3 40.0 1 0 0 4 55.0 30.0 0 1 1 5 44.0 24.0 0 1 0 6 36.7 20.0 0 0 1 7 31.4 17.1 0 0 0 8 27.5 10.0 timing and window generation section all timing is referenced to the vertical and horizontal sync inputs that come in on pins 11 and 12 respectively. the two registers near the inputs sets the start of the window for both the horizontal and vertical direction. the window generator and the following logic are used to generate a pulse to control the video switch used to switch between the video with emphasis and the standard video. the switching be- tween the two video channels is the generation of the win- dow seen by the user. there is the option to switch off the hi-brite window. an additional switch located just before the video switch is used to turn off the control signal. video detection is another important function inside the lm1270. note that both video channels, the pll, and both vertical sync and horizontal flyback signals all go to this block. from these inputs the video detection is used to detect the length of the horizontal and vertical front porch as well as the length of the active video for both the horizontal and vertical directions. this information allows the monitor designer to offer auto alignment in his monitor. further pro- cessing of the video information in the video and window timing data section generates an internal clamp pulse. this is the dc restoration pulse for the lm1270. pin 24 is the output for the clamp pulse, allowing the monitor designer to use it for the clamp input of the pre-amp. there is also the option to program the lm1270 to accept an external clamp pulse instead of using its own internally generated pulse. the video detection section also has a data receiver for receiving data encoded on the video. when this feature is used, the mcu in the monitor is used to control the lm1270, keeping all communication with the lm1270 within the moni- tor. this results in a faster response time by eliminating the need for the computer to control the lm1270. control by the computer requires communication through the monitor mcu. lm1270 www.national.com 8
functional description (continued) using the data encoded on the video eliminates one stage of communicating with the lm1270, allowing for a faster re- sponse time for changes in the hi-brite window. v ref proper operation of the lm1270 does require a very accu- rate reference voltage. this voltage is generated in the v ref block. to insure an accurate voltage over temperature, an external resistor is used to set the current in the v ref stage. the external resistor is connected to pin 23. this resistor should be 1% and have a temperature coefficient under 100 ppm/?c. all video signals must be kept away from pin 23. this pin has a very high input impedance and will pick up any high frequency signals routed near it. the board layout shown in figure 12 is a good example of trace routing near pin 23. the output of the v ref stage goes to a number of blocks in the video section and also to pin 22. this pin allows capacitor filtering on the v ref output and offers an accurate external reference. a buffer must be used with this reference, the maximum current loading should be only 100 a. pin 22 is bi-directional, allowing the lm1270 to be referenced to a pre-amp v ref . this configuration makes it possible to dc couple to the pre-amp, but for accurate dc level, it is recommended that ac coupling be used between the lm1270 and the pre-amp. it is also recommended that the internal v ref be used for best performance. note: any noise injected into pin 22 will appear on the video. the voltage reference must be kept very clean for best perfor- mance of the lm1270. h flyback h flyback is an analog signal input from the monitor hori- zontal scan. this flyback signal goes to the internal horizon- tal flyback pulse generation circuit. an optional capacitor and/or resistor to ground may be needed if noise interferes with the h flyback signal or if there is ringing on the h flyback signal. note: there is no blanking pedestal on the output video. if horizontal blanking is to be added to the video signal it must be done at the pre-amp. r limit is used to limit the input current into the ic to a maximum value of +1 ma during flyback and ?100 a during normal forward scan. for example if an h flyback with a peak of 100v is used, r limit = 100 k ? . the internal input imped- ance of pin 16 is low to limit the maximum voltage swing at the input to be within the supply rail and ground. figure 2 shows the h flyback waveforms and the location of r limit .a 56 pf capacitor has been added to the h flyback pin for filtering noise on the h flyback signal. vertical blanking a similar vertical pulse generation circuit to the lm1238 is included internal to the lm1270. the leading edge of the vertical sync is used to start the programmable vertical blanking signal directly. the vertical blank duration control register sets the width of the pulse. when vertical blanking is enabled its polarity is programmable. clamping pin 24, the clamp pin, can be set for either an input or and output. if used as an input, then this pin functions just like the clamp input pins to the video pre-amps. one should use a series 1 k ? resistor to pin 24 and a small capacitor may also be needed between pin 24 and ground to filter high fre- quency noise. 20063519 figure 2. h flyback input pulse lm1270 www.national.com 9
functional description (continued) the lm1270 has the counters required to locate the clamp pulse to any position on the horizontal line. normally this pin would be used as an output and be connected to the video pre-amps. now the clamp pulse location can be optimize for the video channel. note: when using this pin as an output a 1k ? series resistor must be used to protect the output stage of the clamp circuit. it is also recommended to connect a 10 k ? resistor between this pin and ground for more reliable operation. video detection modes of operation three modes of operation are possible with the video detect circuit: 1. autosizing mode: in this mode the lm1270 takes the measurements necessary for the monitor to perform the autosizing operation. the horizontal flyback is used as the reference for timing. the resultant horizontal outputs are the flyback time, the position of the start of video relative to the flyback end and the time from the end of the active video to the start of the flyback time. since the total line time is known the microcontroller can calculate the active video time. now the microcontroller can cen- ter the video between the start and end of flyback for best image centering, and to calculate the duty cycle of the video with respect to the forward scan time, thus giving a measure of the relative size of the image. for best performance in autosizing mode, it is recom- mended that the maximum pixels per line mode is used when measurements are made. 2. window calibration mode: in this mode, the horizontal sync is used as the reference for timing. the resultant horizontal outputs are the horizontal sync time and the back porch and active image video time that can subse- quently be used in conjunction with the image position data. the image pixel per line value should be used to set the pll. 3. video data transfer: in this mode, data is sent from the pc to the monitor on the first active video line. a 72 pulse clock string is sent on one video channel. data is sent on a second video channel. a window signal that tracks the actual highlight window is sent on the third video chan- nel. the timing parameters of this window signal are timed by the video detect logic and stored in a special register set. the relationship between these three sig- nals is shown in figure 3 . the selection of which video channel contains which signal is programmed by the d_cntl register. image calibration mode two registers are used for each axis to control the window enable signal, win_en. the first register hw_start (vw_start) defines the period in pixels (lines) from the leading edge of the hsync (vsync) to the start of the window. the second register hw_end (vw_end) defines the dura- tion of the highlight window. each of these registers is de- fined as two byte values, as per the table below: the microcontroller must write the values of these registers, after it has received the window position information from the pc. however, the pc may reference this information in any of the following ways: 1. leading edge of sync 2. trailing edge of sync 3. start of the video image in order to accommodate different modes of operation, the video detect function may be used to measure the sync width, and the back porch (i.e., trailing edge of sync to start of video) periods in horizontal pixels, or vertical lines for window position calibration. the video detect function must be set to measure with reference to the horizontal sync. if the leading edge of sync is used as the reference for the window start timing from the pc application, then the start values can be directly written to the registers hw_start and vw_start. if the trailing edge of sync is used as the reference for the window start timing from the pc application, then the micro- controller should add the measured sync durations from the video detect registers to the timing values supplied by the pc application before writing to the hw_start and vw_start registers. if the start of video image is used as the reference for the window start timing from the pc application, then the micro- controller will add the measured sync duration and the back porch duration from the video detect registers to the timing values supplied by the pc application before writing to the hw_start and vw_start registers. in each case, it may also be necessary to modify the window position values by adding or subtracting a value to compen- 20063520 figure 3. data, clock and window signals lm1270 www.national.com 10
video detection (continued) sate for clocking delays in the timing counters in the lm1270. this value is empirically derived from testing the video system. video input detection the outputs of the three video detector channels are or?d together to provide a single composite signal of the three channels when used for timing parameter measurement. the video detect logic must find the extreme points of the displayed image during each frame with respect to the hori- zontal and vertical flyback pulses as measured using the internal pll. for best performance in autosizing mode, it is recommended that the application use the maximum number of pixels per line when measurements are made. remem- ber, the vco frequency is limited to 160 mhz when the prescaler is set to 7. the durations to be measured are shown generically in the figures below, and apply to both horizontal and vertical tim- ings. for the horizontal timings the measurements will de- pend on the mode selected in the emphasis register. ver- tical and hflyback timing measurements will be the same in both modes. 1. flyback or sync period: the duration of either the sync input or the horizontal flyback, in either horizontal lines (vertical) or pixels (horizontal). 2. back porch period: the duration between the trailing edge of the sync or flyback pulse and the leading edge of the first detected video, in either lines (vertical) or pixels (horizontal). 3. video period: the duration between the leading edge of the first detected video and the trailing edge of the last detected video, in either lines (vertical) or pixels (hori- zontal). 4. front porch: the duration between the trailing edge of the last detected video and the leading edge of the sync or flyback pulse, in either lines (vertical) or pixels (hori- zontal). note: in the horizontal timing measurement description, reference to sync means either hsync or h_feedback, selected by wche bit in the emphasis register. as the video may start and finish at different positions on the screen, depending upon the image, the measured horizontal porches and video time may vary from line to line. to over- come this, the periods should be measured over at least one entire field. the hardware records the shortest back porch and front porch periods used over the measured period. window coordinate data the microcontroller must program the highlight window co- ordinates in the lm1270 by writing to the appropriate regis- ters. the coordinate values must be sent from the pc. for maximum flexibility, the lm1270 is designed to allow opera- tion such that the coordinate data may be sent by: 1. ddc2a/b (e.g., i 2 c compatible) transmission 2. information carried as video data during the vertical blanking time 3. any other pc-monitor interface (e.g., usb) coordinate data transmission by video operation when sending coordinate data by video please refer to the information for register 27 in the register descriptions. any video line may be selected for data, clock, or window. it is important to make sure each video line has a different se- lection otherwise the video transmission of data will not function. it is possible to program two video channels to carry the same information and create this incorrect opera- tion. if the limit bit of the test1 register is set to a ?1? (default value), then one line of data may be transmitted after the vertical sync on one of the video channels. this data must be sent during the vertical blanking time that is set by the vertical blanking register. data must be transmitted only during the vertical blanking time otherwise it will be ignored by the logic. if the limit bit of the test1 register is set to a ?0?, then the data may be transmitted at any time following the vertical sync. the data consists of a stream of 9 bytes. in normal use it is expected that the first eight bytes will be data, and the remaining byte will be used as a checksum. alternatively, the ninth byte may be used as an additional data byte. another video channel provides a clock pulse stream of exactly 72 pulses. the logic counts the number of pulses between two horizontal sync pulses. if the number of clock pulses is greater or less than 72, then the data is ignored. if the count is 72, then the data is shifted into registers 2e-36 upon arrival of the next horizontal sync, provided the output 20063521 figure 4. timing intervals with wche = 1 20063522 figure 5. timing intervals with wche = 0 lm1270 www.national.com 11
video detection (continued) registers have been enabled either by previously reading the d_cntls register, or by writing a zero to the stat bit of the d_cntl register. only one line of data is allowed per field. after the clock stream of 72 pulses has been detected and accepted and the data stored in registers 2e-36, no more data will be accepted until after the registers have been reset. this is to allow time for the microcontroller to access the data on the i 2 c bus. if the limit bit in the test1 register is set to a ?1? (default value), then the data must arrive during the pro- grammed vertical blanking period. any data arriving outside of this will be ignored. if the bit is set to a ?0?, then the data may arrive anytime, even within the active video area. the maximum data rate is half of the clock rate. the data is clocked by the trailing edge of the clock. the clock rate should be chosen to allow all 72 pixels to occur within the normal horizontal active video timing. interrupt signal pin 15, the blanking/interrupt pin, can be set to output an interrupt signal by bit 2 of register 39. the default value for this bit is ?0?, setting pin 15 for a blanking output signal. however, if bit 2 is set to a ?1? then pin 15 outputs an interrupt signal. when the lm1270 is instructed to read the information sent by video, then this signal goes low. once the clock stream of 72 pulses has occurred, then the inter- rupt signal goes high again at the leading edge of h sync. the interrupt signal remains high until another request to read the video information is received. some microcontrol- lers may require an interrupt signal. setting pin 15 to output an interrupt signal will provide the needed signal for these systems. in this mode of operation the vertical blanking signal will be unavailable; however, vertical blanking may still be added to the video outputs. note that bit 1 of register 1 does change the polarity of the interrupt signal. parameter timing t clk 50 ns t clk-h 25 ns t clk-l 25 ns t setup-h 13 ns t setup-l 13 ns emphasis measuring emphasis two adjustments are available to optimize the emphasis in the hi-brite window for the various timing modes and bright- ness levels. one adjustment is the center frequency and the other adjustment is the amount of overshoot. referring to figure 7 the overshoot is the ratio of the overshoot voltage to the video level after the emphasis has settle out of the output signal. the typical output level is 900 mv and the typical overshoot is about 20%. the peak measurement is taken 9 ns from the rising edge. this delay gives a more accurate peak measurement by avoiding any ringing that may occur at the rising edge. overshoot is defined in percent as: bits 0 to 2 in register 0b control the emphasis. when a ?4? is programmed into these bits the overshoot is typically 11%. a ?0? will give no overshoot in the hi-brite window. shown below in figure 8 is how the center frequency is measured. the center frequency is actually expressed as the time it takes the overshoot to settle to within 5% of the dc level of the pulse. 20063523 figure 6. timing parameters 20063525 figure 7. overshoot measurement 20063526 figure 8. center frequency measurement lm1270 www.national.com 12
emphasis (continued) bits 0 to 3 in register 0c control the center frequency. when an ?8? is programmed into the register the t center freq is typically 80 ns. an ?f? will give about 145 ns. a ?0? will give no emphasis in the hi-brite window. esd and arc-over protection the lm1270 incorporates full esd protection with special consideration given to maximizing arc-over robustness. the monitor designer must still use good circuit design and pcb layout techniques. the human body model esd susceptibil- ity of the lm1270 is 3.5 kv, however, many monitor manu- facturers are now testing their monitors to level 4 of the iec 801-2 specification which requires the monitor to survive an 8 kv discharge. external esd protection is needed to sur- vive this level of esd. the lm1270 provides excellent pro- tection against both esd and arc-over, but this is not a substitute for good pcb layout. figure 9 shows the recommended input protection for the lm1270. this provides the best protection against esd. when this protection is combined with a good pcb layout the lm1270 will easily survive the iec 801-2 level 4 testing (8 kv esd). it is strongly recommended that the protection diodes be added as shown in figure 9 . the 1n4148 diode has a maximum capacitance of 4 pf which will have little effect on the response of the video system due to the low impedance of the input video. the esd cells of the lm1270 also provide good protection against arc-over, however good pcb layout is necessary. the lm1270 should not be exposed directly to the voltages that may occur during arc-over. the main vulnerability of the lm1270 to arc-over is through the ground traces on the pcb. for proper protection all ground connections associ- ated with the lm1270, including the grounds to the bypass capacitors, must have short returns to the ground pins. a significant ground plane should be used to connect all the lm1270 grounds. figure 12 , which shows the demo board layout, is an excellent example of an effective ground plane. figures 10, 11 are the schematic to the demo board. the list below should be followed to ensure a pcb with good grounding: all grounds associated with the lm1270 should be con- nected together through a large ground plane. crt driver ground is connected to the lm1270 and video pre-amp ground area at one point. crt and arc protection grounds are connected directly to the chassis or main ground. there is no arc-over current flow from these grounds through the lm1270 grounds. input signal traces for sda, scl, h flyback, and sync inputs should be kept away from the crt driver and all traces that could carry the arc current. output signal traces of the lm1270 should be kept away from the traces that carry the output signals of the crt driver. if any one of the above suggestions is not followed the lm1270 may become more vulnerable to arc-over. improper grounding is by far the most common cause of a video pre-amp failure during arc-over. 20063527 figure 9. recommended video input esd protection lm1270 www.national.com 13
20063528 figure 10. lm1270, lm1237/47, lm2465 neck board, page 1 lm1270 www.national.com 14
20063529 figure 11. lm1270, lm1237/47, lm2465 neck board, page 2 lm1270 www.national.com 15
20063530 figure 12. lm1270, lm1237/47, lm2465 neck board lm1270 www.national.com 16
microcontroller interface the microcontroller interfaces to the lm1270 pre-amp via an i 2 c compatible interface. the protocol of the interface begins with the start pulse followed by a byte comprised of a seven-bit slave device address and a read/write bit as the lsb. therefore the address of the lm1270 for writing is 54h (0101 0100) and the address for reading is 55h (0101 0101). figures 13, 14 show a write and read sequence across the i 2 c compatible interface. write sequence the write sequence begins with a start condition which consists of the master pulling sda low while scl is held high. the slave device address is sent next. the address byte is made up of an address of seven bits (7?1) and the read/write bit (0). bit 0 is low to indicate a write operation. each byte that is sent is followed by an acknowledge. when scl is high the master will release the sda line. the slave must pull sda low to acknowledge. the address of the register to be written to is sent next. following the register address and the acknowledge bit the data for the register is sent. if bit 0 of register 0ah is set low (default value) then the lm1270 is set for the increment mode. in this mode when more than one data byte is sent it is automatically incre- mented into the next address location. see figure 13 . note that each data byte is followed by an acknowledge bit. read sequence read sequences are comprised of two i 2 c compatible trans- fer sequences: the first is a write sequence that only trans- fers the address to be accessed. the second is a read sequence that starts at the address transferred in the previ- ous address write access and incrementing to the next ad- dress upon every data byte read. this is shown in figure 14 . the write sequence consists of the start pulse, the slave device address including the read/write bit (a zero, indicat- ing a write), then its acknowledge bit. the next byte is the address to be accessed, followed by its acknowledge bit and the stop bit indicating the end of the address only write access. next the read data access is performed beginning with the start pulse, the slave device address including the read/ write bit (a one, indicating a read) and the acknowledge bit. the next 8 bits will be the data read from the address indicated by the write sequence. subsequent read data bytes will correspond to the next increment address loca- tions. each data byte is separated from the other data bytes by an acknowledge bit. 20063531 figure 13. i 2 c compatible write sequence lm1270 www.national.com 17
microcontroller interface (continued) i 2 c compatible interface registers ic address for i 2 c compatible bus slave address of the lm1270 is 54h when writing to the registers and 55h when reading from the registers. register add deflt 76543210 i_o0 00 00 vdt hsy/fb reset black vclb pwrsv sel/wb a/b_sel i_o1 01 08 cl pol cl i/o bl pol blank vbl en rsv vsy pol hsy pol cl_pos0 02 00 clp7 clp6 clp5 clp4 clp3 clp2 clp1 clp0 cl_pos1 03 00 clp9 clp8 cl_dur 04 04 cld7 cld6 cld5 cld4 cld3 cld2 cld1 cld0 not used 05 00 rsv rsv rsv rsv rsv rsv rsv rsv not used 06 00 rsv rsv not used 07 00 rsv rsv rsv rsv rsv rsv rsv rsv v_bl_du 08 0f vb6 vb5 vb4 vb3 vb2 vb1 vb0 acont 09 52 rsv acon6 acon5 acon4 acon3 acon2 acon1 acon0 bcont 0a 52 rsv bcon6 bcon5 bcon4 bcon3 bcon2 bcon1 bcon0 emphasis 0b 00 win_sel vref wche wghe rsv emp2 emp1 emp0 cnt_f 0c 08 centf3 centf2 centf1 centf0 ppl0 0d ff ppl7 ppl6 ppl5 ppl4 ppl3 ppl2 ppl1 ppl0 ps_ppl1 0e 7f auto presc2 presc1 presc0 frerun ppl10 ppl9 ppl8 hw_st0 0f 00 hw_st7 hw_st6 hw_st5 hw_st4 hw_st3 hw_st2 hw_st1 hw_st0 hw_st1 10 00 hw_st10 hw_st9 hw_st8 hw_end0 11 00 hw_en7 hw_en6 hw_en5 hw_en4 hw_en3 hw_en2 hw_en1 hw_en0 hw_end1 12 00 hw_en10 hw_en9 hw_en8 vw_st0 13 00 vw_st7 vw_st6 vw_st5 vw_st4 vw_st3 vw_st2 vw_st1 vw_st0 vw_st1 14 00 vw_st10 vw_st9 vw_st8 vw_end0 15 00 vw_en7 vw_en6 vw_en5 vw_en4 vw_en3 vw_en2 vw_en1 vw_en0 20063532 figure 14. i 2 c compatible read sequence lm1270 www.national.com 18
i 2 c compatible interface registers (continued) register add deflt 76543210 vw_end1 16 00 vw_en10 vw_en9 vw_en8 h_fp0 17 ff hfp7 hfp6 hfp5 hfp4 hfp3 hfp2 hfp1 hfp0 h_fp1 18 07 hfp10 hfp9 hfp8 hf_s0 19 ff hfl_hs7 hfl_hs6 hfl_hs5 hfl_hs4 hfl_hs3 hfl_hs2 hfl_hs1 hfl_hs0 hf_s1 1a 03 hfl_hs9 hfl_hs8 h_bp0 1b ff hbp7 hbp6 hbp5 hbp4 hbp3 hbp2 hbp1 hbp0 h_bp1 1c 07 hbp10 hbp9 hbp8 v_fp0 1d ff vfp7 vfp6 vfp5 vfp4 vfp3 vfp2 vfp1 vfp0 v_fp1 1e 07 vfp10 vfp9 vfp8 v_syn_d 1f ff vsync7 vsync6 vsync5 vsync4 vsync3 vsync2 vsync1 vsync0 v_bp0 20 ff vbp7 vbp6 vbp5 vbp4 vbp3 vbp2 vbp1 vbp0 v_bp1 21 07 vbp10 vbp9 vbp8 v_fp0_prv 22 ff vfp7 vfp6 vfp5 vfp4 vfp3 vfp2 vfp1 vfp0 v_fp1_prv 23 07 vfp10 vfp9 vfp8 v_syn_d_prv 24 ff vsync7 vsync6 vsync5 vsync4 vsync3 vsync2 vsync1 vsync0 v_bp0_prv 25 ff vbp7 vbp6 vbp5 vbp4 vbp3 vbp2 vbp1 vbp0 v_bp1_prv 26 07 vbp10 vbp9 vbp8 d_cntl 27 00 stat wd g1 g0 b1 b0 r1 r0 hw_sm0 28 00 hwsm7 hwsm6 hwsm5 hwsm4 hwsm3 hwsm2 hwsm1 hwsm0 hw_sm1 29 00 hwsm10 hwsm9 hwsm8 hw_s0 2a 00 hws7 hws6 hws5 hws4 hws3 hws2 hws1 hws0 hw_s1 2b 00 hws9 hws8 hw_dm0 2c 00 hwdm7 hwdm6 hwdm5 hwdm4 hwdm3 hwdm2 hwdm1 hwdm0 hw_dm1 2d 00 hwdm10 hwdm9 hwdm8 hw_dat0 2e 00 hwd07 hwd06 hwd05 hwd04 hwd03 hwd02 hwd01 hwd00 hw_dat1 2f 00 hwd17 hwd16 hwd15 hwd14 hwd13 hwd12 hwd11 hwd10 hw_dat2 30 00 hwd27 hwd26 hwd25 hwd24 hwd23 hwd22 hwd21 hwd20 hw_dat3 31 00 hwd37 hwd36 hwd35 hwd34 hwd33 hwd32 hwd31 hwd30 hw_dat4 32 00 hwd47 hwd46 hwd45 hwd44 hwd43 hwd42 hwd41 hwd40 hw_dat5 33 00 hwd57 hwd56 hwd55 hwd54 hwd53 hwd52 hwd51 hwd50 hw_dat6 34 00 hwd67 hwd66 hwd65 hwd64 hwd63 hwd62 hwd61 hwd60 hw_dat7 35 00 hwd77 hwd76 hwd75 hwd74 hwd73 hwd72 hwd71 hwd70 hw_dat8 36 00 hwd87 hwd86 hwd85 hwd84 hwd83 hwd82 hwd81 hwd80 d_cntls 37 00 stat wd g1 g0 b1 b0 r1 r0 test0 38 00 rsv rsv tee rsv rsv bce rsv rsv test1 39 chgrg rsv rdir irpt aid bl/int limit intlc register descriptions inputs and outputs controls ? 0 register addr 7 6 5 4 3 2 1 0 i_o0 00 vdt hsy/fb reset black vclb pwrsv sel/wb a/b_sel bit 0: selects the active input provided bit 1 of this register is 0. if bit 0 = 0, input source b is selected (default) if bit 0 = 1, input source a is selected bit 1: controls whether the input source is selected by bit 0, or by the window function if bit 1 = 0, bit 0 source select is selected (default) if bit 1 = 1, window function is selected bit 2: sends the device into power save mode. this register bit is fed to the preamplifier interface as pwr_save so that the amplifier can be put into low power sleep mode. it is also or?d with the blanking signals to set the blank output level to the lm1270 www.national.com 19
register descriptions (continued) selected blank level, and to set the video output to black level to blank the video. if bit 2 = 0, enable the analog circuits for normal operation (default) if bit 2 = 1, send the device into power save mode bit 3: video detect enable: when this bit is set to 1, this enables the video detection logic and video detectors to run. default: 0 bit 4: set the output to the black level if bit 4 = 0, normal video (default) if bit 4 = 1, video set to black level bit 5: full ic reset: this is a self resetting bit. whe na1is written to this bit, the ic is reset. the bit automatically returns to 0 after reset has occurred. if bit 5 = 0, normal (default) if bit 5 = 1, reset bit 6: selects whether hflyback or hsync is measured and used as the timing reference during video detect if bit 6 = 0, hsync is selected (default) if bit 6 = 1, hflyback is selected bit 7: video detect reset: this is a self resetting bit. whe na1is written to this bit, the video detect registers are reset to start a new timing cycle. the bit automatically returns to 0 after reset has occurred. if bit 7 = 0, normal (default) if bit 7 = 1, reset inputs and outputs controls ? 1 register addr 7 6 5 4 3 2 1 0 i_o1 01 cl pol cl i/o bl pol blank vbl en rsv vsy pol hsy pol bit 0: selects the h sync input polarity if bit 0 = 0, positive h sync input signal required. (default) if bit 0 = 1, negative h sync input signal required. bit 1: selects the v sync input polarity if bit 1 = 0, positive v sync input signal required. (default) if bit 1 = 1, negative v sync input signal required. bit 2: reserved bit 3?4: blanking operation: bit4 bit3 blank/interrupt output pin 0 0 no blank signal 0 1 vertical blanking only (default) 1 x blank bit 5: selects the blank or interrupt signal output polarity if bit 4 = 0, positive active. (default) if bit 4 = 1, negative active bit 6: determines whether the clamp pin is an input or output if bit 6 = 0, input (default) if bit 6 = 1, output bit 7: selects the clamp output or input active level polarity if bit 7 = 0, positive active. (default) if bit 7 = 1, negative active clamp position register addr 76543210 cl_pos0 02 clp7 clp6 clp5 clp4 clp3 clp2 clp1 clp0 cl_pos1 03 clp9 clp8 this is a 10 bit wide register that sets the position of the clamp pulse with respect to the leading edge of the h sync pulse in increments of 2 cycles of the main pll pixel clock. lm1270 www.national.com 20
register descriptions (continued) clamp duration register addr 76543210 cl_dur 04 cld7 cld6 cld5 cld4 cld3 cld2 cld1 cld0 this is an 8 bit wide register that sets the width of the active clamp pulse in increments of 2 cycles of the main pll pixel clock. registers 05?07 are not used register addr 76543210 not used 05 rsv rsv rsv rsv rsv rsv rsv rsv not used 06 rsv rsv not used 07 rsv rsv rsv rsv rsv rsv rsv rsv registers 05?07 are not used. however, data can be written to these registers and read back from these registers at the ?rsv? locations. any data written to these registers will not affect the operation of the lm1270. v blank duration register addr 7 6543210 v_bl_du 08 vb6 vb5 vb4 vb3 vb2 vb1 vb0 this i s a 7 bit wide register that sets the width of the active v blank pulse in horizontal line periods. input a contrast register addr 7 6543210 acont 09 ablnk acon6 acon5 acon4 acon3 acon2 acon1 acon0 bit 0?6: this i s a 7 bit wide register that sets the contrast level of input a. when the register is zero, the output is at minimum contrast. bit 7: setting this bit sets the input a only to black level. if bit 7 = 0, normal video. (default) if bit 7 = 1, input a set to black level input b contrast register addr 7 6543210 bcont 0a bblnk bcon6 bcon5 bcon4 bcon3 bcon2 bcon1 bcon0 bit 0?6: this i s a 7 bit wide register that sets the contrast level of input b. when the register is zero, the output is at minimum contrast. bit 7: setting this bit sets the input b only to black level. if bit 7 = 0, normal video. (default) if bit 7 = 1, input b set to black level emphasis register addr 7 6 5 4 3 2 1 0 emphasis 0b win_sel vref wche wghe rsv emp2 emp1 emp0 bit 2?0: this i s a 3 bit wide register that sets the emphasis level of input b. when this value is zero, no emphasis is applied. bit 3: reserved. bit 4: this bit controls the horizontal edge used to start the pixel counters in the dynamic window generation block and video data transfer detect block. if bit 4 = 0, h_feedback which is in sync with pll, is used for the edge. if bit 4 = 1, hsync synchronized to pixel clock is used as the edge. bit 5: this bit controls the horizontal edge used to start the pixel counters in the window calibration block. if bit 5 = 0, h_feedback which is in sync with pll, is used for the edge. if bit 5 = 1, hsync synchronized to pixel clock is used as the edge. note: two separate bits are used in case these blocks need to be in different modes. bit 6: this bit controls which source is selected for the reference voltage v ref . if bit 6 = 0, internal v ref is selected. (default) if bit 6 = 1, external v ref is selected lm1270 www.national.com 21
register descriptions (continued) bit 7: this bit controls which source is selected for inside the window, and which source is outside. if bit 7 = 0, input b is inside the window. (default) if bit 7 = 1, input b is outside the window emphasis center frequency register addr 7 6 5 4 3210 cnt_f 0c centf3 centf2 centf1 centf0 this i s a 4 bit wide register that sets the center frequency of the emphasis filter. when the value is zero, the center frequency is set to its minimum value. pixels per line/prescaler register addr 7 6 5 4 3 2 1 0 ppl0 0d ppl7 ppl6 ppl5 ppl4 ppl3 ppl2 ppl1 ppl0 ps_ppl1 0e auto presc2 presc1 presc0 frerun ppl10 ppl9 ppl8 bit 10?0: sets the pixel per line value for the pll and window function bit 14?12: sets prescaler value for the pll bit 15: sets the prescaler to automode. when set for automode the lm1270 automatically selects the optimum value for the prescaler. bits 12?14 will be the starting point for automode. horizontal window start position register addr 76543 2 10 hw_st0 0f hw_st7 hw_st6 hw_st5 hw_st4 hw_st3 hw_st2 hw_st1 hw_st0 hw_st1 10 hw_st10 hw_st9 hw_st8 this is an 11 bit wide register that sets the horizontal position in number of pixels of the b select window pulse with respect to the leading edge of the h sync pulse. horizontal window duration register addr 76543 2 10 hw_end0 11 hw_en7 hw_en6 hw_en5 hw_en4 hw_en3 hw_en2 hw_en1 hw_en0 hw_end1 12 hw_en10 hw_en9 hw_en8 this is an 11 bit wide register that sets the horizontal duration in number of pixels of the b select window pulse. if this value is zero, the window is disabled. vertical window start position register addr 76543 2 10 vw_st0 13 vw_st7 vw_st6 vw_st5 vw_st4 vw_st3 vw_st2 vw_st1 vw_st0 vw_st1 14 vw_st10 vw_st9 vw_st8 this is an 11 bit wide register that sets the vertical position in number of lines of the b select window pulse with respect to the leading edge of the v sync pulse. vertical window duration register addr 76543 2 10 vw_end0 15 vw_en7 vw_en6 vw_en5 vw_en4 vw_en3 vw_en2 vw_en1 vw_en0 vw_end1 16 vw_en10 vw_en9 vw_en8 this is an 11 bit wide register that sets the vertical duration of the b select window pulse in number of lines. if this value is zero, the window is disabled. horizontal front porch duration register addr 76543 2 10 h_fp0 17 hfp7 hfp6 hfp5 hfp4 hfp3 hfp2 hfp1 hfp0 h_fp1 18 hfp10 hfp9 hfp8 this is an 11 bit wide register that records the lowest measured value of the horizontal front porch in number of pixels during video detect. when no video is detected, this register will return a value of zero. reading this register within less than one complete field period after the video detect reset may give erroneous results. this register resets to zero after the video detect reset has been written. lm1270 www.national.com 22
register descriptions (continued) horizontal flyback or sync duration register addr 76543210 hf_s0 19 hfl_hs7 hfl_hs6 hfl_hs5 hfl_hs4 hfl_hs3 hfl_hs2 hfl_hs1 hfl_hs0 hf_s1 1a hfl_hs9 hfl_hs8 this is a 10 bit wide register that records the measured value of the horizontal flyback or sync in number of pixels during video detect. reading this register within less than one complete field period after the video detect reset may give erroneous results. this register resets to zero after the video detect reset has been written. horizontal back porch duration register addr 76543 2 10 h_bp0 1b hbp7 hbp6 hbp5 hbp4 hbp3 hbp2 hbp1 hbp0 h_bp1 1c hbp10 hbp9 hbp8 this is an 11 bit wide register that records the lowest measured value of the horizontal front porch in number of pixels during video detect. when no video is detected, the sum of this register and the hflyback/hsync should be within 1 pixel of the total number of pixels per line. reading this register within less than one complete field period after the video detect reset may give erroneous results. this register resets to zero after the video detect reset has been written. vertical front porch duration register addr 76543 2 10 v_fp0 1d vfp7 vfp6 vfp5 vfp4 vfp3 vfp2 vfp1 vfp0 v_fp1 1e vfp10 vfp9 vfp8 this is an 11 bit wide register that records the lowest measured value of the vertical front porch during video detect in horizontal line periods. when no video is detected, this register will return a value of zero. reading this register within less than one complete field period after the video detect reset may give erroneous results. this register resets to zero after the video detect reset has been written. vertical sync duration register addr 76543210 v_syn_d 1f vsync7 vsync6 vsync5 vsync4 vsync3 vsync2 vsync1 vsync0 this is an 8 bit wide register that records the measured value of the vertical sync during video detect in horizontal line periods. reading this register within less than one complete field period after the video detect reset may give erroneous results. this register resets to zero after the video detect reset has been written. vertical back porch duration register addr 76543 2 10 v_bp0 20 vbp7 vbp6 vbp5 vbp4 vbp3 vbp2 vbp1 vbp0 v_bp1 21 vbp10 vbp9 vbp8 this is an 11 bit wide register that records the lowest measured value of the vertical back porch during video detect in horizontal line periods. when no video is detected, the sum of this register and the vsync should be within 1 line of the total number of lines per field. reading this register within less than one complete field period after the video detect reset may give erroneous results. this register resets to zero after the video detect reset has been written. previous field vertical front porch duration register addr 76543 2 10 v_fp0_prv 22 vfp7 vfp6 vfp5 vfp4 vfp3 vfp2 vfp1 vfp0 v_fp1_prv 23 vfp10 vfp9 vfp8 this is an 11 bit wide register that retains the previous lowest measured value of the vertical front porch during video detect in horizontal line periods from the previous field. it is used when interlace mode is present, in order to accurately determine the correct parameter value for the frame. when no video is detected, this register should return a value of zero. reading this register within less than one complete field period after the video detect reset may give erroneous results. this register resets to zero after the video detect reset has been written. previous field vertical sync duration register addr 76543210 v_syn_d_prv 24 vsync7 vsync6 vsync5 vsync4 vsync3 vsync2 vsync1 vsync0 lm1270 www.national.com 23
register descriptions (continued) this is an 8 bit wide register that records the previous measured value of the vertical sync during video detect in horizontal line periods from the previous field. it is used when interlace mode is present, in order to accurately determine the correct parameter value for the frame. reading this register within less than one complete field period after the video detect reset may give erroneous results. this register resets to zero after the video detect reset has been written. previous field vertical back porch duration register addr 76543 2 10 v_bp0_prv 25 vbp7 vbp6 vbp5 vbp4 vbp3 vbp2 vbp1 vbp0 v_bp1_prv 26 vbp10 vbp9 vbp8 this is an 11 bit wide register that records the previous lowest measured value of the vertical back porch during video detect in horizontal line periods from the previous field. it is used when interlace mode is present, in order to accurately determine the correct parameter value for the frame. when no video is detected, the sum of this register and the vsync should be within 1 line of the total number of lines per field. reading this register within less than one complete field period after the video detect reset may give erroneous results. this register resets to zero after the video detect reset has been written. data control register addr 7 6 5 4 3 2 1 0 d_cntl 27 stat wd g1 g0 b1 b0 r1 r0 bit 5?0: this sets the selection for each video line function when reading data, according to the following table, where x = r, g, or b: x1 x0 function 0 0 not selected 0 1 data 1 0 clock 1 1 window note that there is nothing to prevent the different bits being set to the same value, resulting in erroneous connection of the video channels. however, if the registers are wrongly programmed, incorrect information will result. default is 00. bit 6: this bit enables the window detect video detect function to detect the horizontal window line during any valid data detection period (as set by bit 1 of the register test1). once set it remains set until turned off. when the first string of 72 clock pulses in one line has been detected, the values of the timed horizontal parameters are strobed into the horizontal window registers, and any further data transfers are ignored until the stat bit is set to 0 again. (default is 0). bit 7: if the number of clock pulses is exactly 72 when h sync arrives, and the clock pulses occurred during a valid period, as defined by bit 1 of register test1, then the data is parallel loaded in a holding register (hw_dat) and the stat bit (bit 7) is set to ?1? in the d_cntl register. this loading only happens if the stat was initially ?0?, otherwise the shift-register data is discarded. the microcontroller reads the d_cntl register and if the stat bit is set, it continues by reading hw_dat registers, otherwise the read is discontinued. if the complete block of data registers is read, then at the end of the data read the microcontroller should read the shadow of d_cntl in register d_cntls, which will clear the stat bit. alternatively, if only certain data registers need to be read, then either the d_cntls register should be read after this action to clear the stat bit, or a ?0? should be written to bit 7 of this register. clearing of the stat bit will then allow the core to update the hw_dat registers during the next valid data transmission period. horizontal window measured start duration register addr 76543 2 10 hw_sm0 28 hwsm7 hwsm6 hwsm5 hwsm4 hwsm3 hwsm2 hwsm1 hwsm0 hw_sm1 29 hwsm10 hwsm9 hwsm8 this is an 11 bit wide register that records the measured value in number of pixels of the duration between the beginning of hsync and the start of the hwindow on the video data window line during any valid data detection period (as set by bit 1 of the register test1), providing the stat bit in d_cnt register is zero. note: only the video detect on the selected window video line is enabled using the d_cntl register. when no video is detected, this register should return a value of zero. reading this register during the period between vsync and the 72 clock pulse transmission may give erroneous results. this register resets to zero after the stat bit in the d_cntls register is read, and not re-enabled until the next vertical sync. also note that all six hwindow related registers must be read before stat can reset them to zero in order to prevent updates during reading. lm1270 www.national.com 24
register descriptions (continued) horizontal window sync duration register addr 76543210 hw_s0 2a hws7 hws6 hws5 hws4 hws3 hws2 hws1 hws0 hw_s1 2b hws9 hws8 this is a 10 bit wide register that records the measured value of the horizontal sync in number of pixels during the vertical blanking time, providing the stat bit in d_cnt register is zero. this register resets to zero after the stat bit in the d_cntls register is read, and not re-enabled until the next vertical sync. also note that all six hwindow related registers must be read before stat can reset them to zero in order to prevent updates during reading. horizontal window measured duration register addr 76543 2 10 hw_dm0 2c hwdm7 hwdm6 hwdm5 hwdm4 hwdm3 hwdm2 hwdm1 hwdm0 hw_dm1 2d hwdm10 hwdm9 hwdm8 this is an 11 bit wide register that records the measured value of the duration of the data window on the selected video line in number of pixels, during any valid data detection period (as set by bit 1 of the register test1). note: only the video detect on the selected window video line is enabled using the d_cntl register. this register resets to zero after the stat bit in the d_cntls register is read, and not re-enabled until the next vertical sync. also note that all six hwindow related registers must be read before stat can reset them to zero in order to prevent updates during reading. horizontal window data register addr 76543210 hw_dat0 2e hwd07 hwd06 hwd05 hwd04 hwd03 hwd02 hwd01 hwd00 hw_dat1 2f hwd17 hwd16 hwd15 hwd14 hwd13 hwd12 hwd11 hwd10 hw_dat2 30 hwd27 hwd26 hwd25 hwd24 hwd23 hwd22 hwd21 hwd20 hw_dat3 31 hwd37 hwd36 hwd35 hwd34 hwd33 hwd32 hwd31 hwd30 hw_dat4 32 hwd47 hwd46 hwd45 hwd44 hwd43 hwd42 hwd41 hwd40 hw_dat5 33 hwd57 hwd56 hwd55 hwd54 hwd53 hwd52 hwd51 hwd50 hw_dat6 34 hwd67 hwd66 hwd65 hwd64 hwd63 hwd62 hwd61 hwd60 hw_dat7 35 hwd77 hwd76 hwd75 hwd74 hwd73 hwd72 hwd71 hwd70 hw_dat8 36 hwd87 hwd86 hwd85 hwd84 hwd83 hwd82 hwd81 hwd80 data control shadow register addr 7 6 5 4 3 2 1 0 d_cntls 37 stat wd g1 g0 b1 b0 r1 r0 this register is a shadow of the d_cntl register. reading this register will cause the stat bit to reset to 0, which will allow new data to be transferred into the window and data registers after the next valid data transmission block. test register 0 register addr 7 6 5 43210 test0 38 rsv rsv tee rsv rsv bce rsv rsv this register is for testing the lm1270 during production. all bits in this register should be set to ?0? for proper operation. test register 1 register addr 7 6 5 4 3 2 1 0 test1 39 chgrg rsv rdir irpt aid bl/int limit intlc bit 0: if this bit is ?0? (default), then normal progressive scan mode is enabled. if set to ?1?, then interlace mode is enabled. bit 1: this bit limits the period during which video data may be detected. if the bit is set t o a 1 (default), then the valid data active period is limited to the vertical blanking time, as set by the vertical blanking register. if a string of 72 clock pulses is received during this time it is accepted as valid. if a string of 72 pulses is not received until during the active video time, then this data is ignored. if the bit is set to ?0?, then the first 72 pulse clock string that is detected is considered to be valid, even if this is during the active video time. lm1270 www.national.com 25
register descriptions (continued) bit 2: if this bit is set to ?0?, then the output blanking/interrupt pin is set to blanking function (default). if the output is set to ?1?, then the output functions as an interrupt following the level set in the stat bit of d_cntl register. bit 3: if this bit is set to ?0? (default), then the i 2 c compatible address is automatically incremented on sequential read or write operations. if this bit is set to ?1?, the automatic increment is disabled. bit 4: if this bit is set to ?0? (default), the video and window interface registers are changed only during vertical blanking. if it is set to ?1?, then the registers can be changed at any time. the registers controlled by this bit are contrast a (09), contrast b (0a), emphasis (0b), center frequency (0c), and the window start and stop positions (0f through 16). bit 5: this is a test register. it should always be set to a ?0? (default) for normal operation. bit 6: reserved. bit 7: when the pll changes its scale, this bit momentarily goes high. lm1270 www.national.com 26
physical dimensions inches (millimeters) unless otherwise noted order number LM1270Na ns package number n24d life support policy national?s products are not authorized for use as critical components in life support devices or systems without the express written approval of the president and general counsel of national semiconductor corporation. as used herein: 1. life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. a critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. national semiconductor americas customer support center email: new.feedback@nsc.com tel: 1-800-272-9959 national semiconductor europe customer support center fax: +49 (0) 180-530 85 86 email: europe.support@nsc.com deutsch tel: +49 (0) 69 9508 6208 english tel: +44 (0) 870 24 0 2171 fran?ais tel: +33 (0) 1 41 91 8790 national semiconductor asia pacific customer support center email: ap.support@nsc.com national semiconductor japan customer support center fax: 81-3-5639-7507 email: jpn.feedback@nsc.com tel: 81-3-5639-7560 www.national.com lm1270 hi-brite 200 mhz i 2 c compatible rgb image enhancer with video auto sizing national does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and national reserves the righ t at any time without notice to change said circuitry and specifications.

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