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AN164
Application Note
LXT310/318 TO CS61310/18 REPLACEMENT GUIDE
1. INTRODUCTION
The purpose of this application note is to provide design suggestions and recommendations for customers wishing to replace Level One Long Haul Line Interface Units (LIUs) with the Cirrus Logic equivalents. Specifically, considerations for replacing the LXT310 T1 Long Haul LIU with the CS61310 are covered; as are considerations for replacing the LXT318 E1 Long Haul LIU with the CS61318. This document is intended to be used in conjuction with the CS61310 and CS61318 data sheets. In short, only the resistors on the receive channel need to be changed if an LXT310 is to be replaced with a CS61310. Otherwise, all circuitry and all software remain the same. There are no changes that need to be performed if an LXT318 is to be replaced with a CS61318. Thus it is very easy to replace the LXT310/318 with Cirrus Logic's CS61310/18 equivalent parts. While the required changes are minimal, users will gain additional functionality inherent to the Cirrus Logic Crystal(R) line of telecommunications ICs. These additional features include:
Crystal-less jitter attenuation User programmable pulse shapes Network loopback signal generation and detection Line quality, LOS and AIS monitoring in all modes
If desired, users may make use of this functionality as detailed in Section 4, Comparisons. The CS61310/18 are 5.0V devices available in both PLCC and PDIP package styles, and are released to high volume production. Customer Evaluation Kits are available for these devices, part number CDB61310/318. For in-depth details regarding theory of operation, please view the respective product data sheets.
Device # CS61310-IL CS61310-IP CS61318-IL CS61318-IP
Description T1 LH LIU T1 LH LIU E1 LH LIU E1 LH LIU
Replaces LXT310PE LXT310NE LXT318PE LXT318NE
Package 28-pin PLCC 28-pin PDIP 28-pin PLCC 28-pin PDIP
Power 5V 5V 5V 5V
Temp. Industrial Industrial Industrial Industrial
Table 1. Cirrus Replacements for Level One Long Haul LIUs
P.O. Box 17847, Austin, Texas 78760 (512) 445 7222 FAX: (512) 445 7581 http://www.cirrus.com
Copyright (c) Cirrus Logic, Inc. 1999 (All Rights Reserved)
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TABLE OF CONTENTS
1. 2. 3. 4. INTRODUCTION ....................................................................................................................... 1 BENEFITS OF FEATURES UNIQUE TO CIRRUS LOGIC ...................................................... 3 FREQUENTLY ASKED QUESTIONS ...................................................................................... 3 COMPARISONS ....................................................................................................................... 4 4.1 Block Diagram: CS61310/18 Shown .................................................................................. 4 4.2 Pinouts ............................................................................................................................... 4 4.2.1 T1 Pinout: CS61310 Shown .................................................................................. 5 4.2.2 E1 Pinout: CS61318 Shown .................................................................................. 6 4.3 Clocking ............................................................................................................................. 7 4.4 Application Modes .............................................................................................................. 8 4.4.1 Hardware mode ..................................................................................................... 8 4.4.2 Host mode ............................................................................................................. 9 4.5 Layout Comparisons ........................................................................................................ 10 4.5.1 T1 Layout Comparison: CS61310 versus LXT310 .............................................. 10 4.5.2 E1 Layout Comparison: CS61318 versus LXT318 ............................................. 11 4.6 Software Expansion: CS61310/18 shown ........................................................................ 12 5. SUMMARY .............................................................................................................................. 12 5.1 Replacing LXT310 with CS61310 .................................................................................... 12 5.2 Replacing LXT318 with CS61318 .................................................................................... 12 6. CONCLUSION ........................................................................................................................ 12
LIST OF FIGURES
Figure 1. CS61310/18 Functional Block Diagram ........................................................................... 4 Figure 2. Typical Hardware-Mode Application for the CS61310/18 ................................................ 8 Figure 3. Typical Host-Mode Application for the CS61310/18 ........................................................ 9 Figure 4. T1 Layout Comparison................................................................................................... 10 Figure 5. E1 Layout Comparison................................................................................................... 11
LIST OF TABLES
Table 1. Cirrus Replacements for Level One Long Haul LIUs ........................................................ 1 Table 2. Clocking options for the Cirrus and Level One Long Haul LIUs ........................................ 7 Table 3. Control Registers of CS61310/61318.............................................................................. 12
Contacting Cirrus Logic Support
For a complete listing of Direct Sales, Distributor, and Sales Representative contacts, visit the Cirrus Logic web site at: http://www.cirrus.com/corporate/contacts/
Preliminary product information describes products which are in production, but for which full characterization data is not yet available. Advance product information describes products which are in development and subject to development changes. Cirrus Logic, Inc. has made best efforts to ensure that the information contained in this document is accurate and reliable. However, the information is subject to change without notice and is provided "AS IS" without warranty of any kind (express or implied). No responsibility is assumed by Cirrus Logic, Inc. for the use of this information, nor for infringements of patents or other rights of third parties. This document is the property of Cirrus Logic, Inc. and implies no license under patents, copyrights, trademarks, or trade secrets. No part of this publication may be copied, reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photographic, or otherwise) without the prior written consent of Cirrus Logic, Inc. Items from any Cirrus Logic website or disk may be printed for use by the user. However, no part of the printout or electronic files may be copied, reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photographic, or otherwise) without the prior written consent of Cirrus Logic, Inc.Furthermore, no part of this publication may be used as a basis for manufacture or sale of any items without the prior written consent of Cirrus Logic, Inc. The names of products of Cirrus Logic, Inc. or other vendors and suppliers appearing in this document may be trademarks or service marks of their respective owners which may be registered in some jurisdictions. A list of Cirrus Logic, Inc. trademarks and service marks can be found at http://www.cirrus.com.
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2. BENEFITS OF FEATURES UNIQUE TO CIRRUS LOGIC
The additional functionality that a user gains by replacing the LXT310/318 with the CS61310/18 includes the following:
n
3. FREQUENTLY ASKED QUESTIONS
n
Is the CS61310 a drop-in replacement for the LXT310, requiring no circuit changes? ANSWER: The use of the CS61310 device in a previously-LXT310 socket requires only one change. The values of the transmit resistors should be changed to 9.1 from the LXT310 requirement of 12.5 . In applications where common mode noise is an issue, Cirrus recommends the addition of a 0.47 F capacitor on the receive circuit (see CS61310 datasheet).
Crystal-less Jitter Attenuation: This feature reduces system cost because the CS61310/18 were designed to meet stringent jitter attenuation specs without the expense of external circuitry. User Programmable Pulse Shapes: This feature allows the user to program the CS61310/18 to compensate for pulse degradation caused by non-standard cables, transformers, or protection circuitry. As a result, the customer saves the time and money associated with tweaking the analog hardware design to achieve T1/E1 pulse shape compliance. In some applications, this feature allows the user to reduce the T1/E1 pulse amplitude as a means to save power. Network Loopback Signal Generation and Detection (Loop Up/Loop Down): These features support enhanced link diagnostics and error detection without requiring human intervention at the far end. Line Quality, LOS and AIS Monitoring Available In All Modes: The CS61310/18's line quality monitor provides the highest line quality resolution of any LIU on the market. Consequently, the user has a much more accurate picture of the line condition. The user also has the flexibility of using either hardware or host mode to monitor the CS61310/18's LOS and AIS status.
n
n
Is the CS61318 a drop-in replacement for the LXT318, requiring no circuit changes? ANSWER: Yes! A CS61318 device can be used in an previously LXT318 socket with NO changes to the circuit. In applications where common mode noise is an issue, Cirrus recommends the addition of a 0.47 F capacitor on the receive circuit (see CS61318 datasheet).
n
n
Are there any software changes required when replacing the LXT310/318 with the CS61310/18? ANSWER: No! There are NO software changes required to use the CS61310/18 in the same manner as the Level One equivalents. However, the CS61310/18 do offer additional functionality, beyond the capabilities of the respective Level One devices. If the user wishes, they can modify their software to access the features unique to Crystal Long Haul LIUs.
n
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4. COMPARISONS 4.1 Block Diagram: CS61310/18 Shown
The functional blocks internal to the CS61310/18 are shown below in Figure 1. "Equalizer Gain Limit". The LXT310 application drawings show this pin as connected to ground, which is an acceptable option for pin 17 of the CS61310. The pinout of the CS61318 differs from that of the LXT318 by one pin, pin 17. The CS61318 data sheet refers to this pin as a "No Connect", while the data sheet for the LXT318 refers to this pin as "GND". This is an acceptable option for pin 17 of the CS61318.
4.2 Pinouts
The pinout of the CS61310 differs from that of the LXT310 by one pin, pin 17. The CS61310 data sheet refers to this pin as a "No Connect", while the data sheet for the LXT310 refers to this pin as
TCLK TDATA/TPOS UBS/TNEG JASEL
2
3
4 11
E N C O D E R
JITTER ATTEN
TRANSMIT TIMING & CONTROL
PULSE SHAPING CIRCUITRY ROM / RAM
13
LINE DRIVERS
TTIP
16 28 26 27 24 25
TRING CLKE/TAOS CS/RLOOP SCLK/LLOOP SDI/LBO 1* SDO/LBO 2*
TAOS Enable REMOTE LOOPBACK LOCAL LOOPBACK (DIGITAL)
LBO Selec t*
SERIAL PORT
REGISTERS & CONTROL LOGIC LOS/ NLOOP Clear LLOOP Enable EQUALIZER CONTROL SLICERS & PEAK DETECT NOISE & CROSSTALK FILTERS
RCLK RDATA/RPOS
BPV/RNEG
D 8E C 7O D 6 E R
LOCAL LOOPBACK (ANALOG) 18 LATN
JITTER ATTEN
TIMING & DATA RECOVERY
MAGNITUDE EQUALIZER
AGC
19 20
RTIP
RRING
INT/NLOOP LOS
23 12
INBAND NLOOP & LOS PROCESSOR 9
RECEIVE CLOCK GENERATOR
1
MCLK
10 XTALOUT
5 MODE
21 RV+
22
14
15 TV+
XTALIN
RGND TGND
* : LBO Select, LBO1 and LBO2 only available on CS61310.
Figure 1. CS61310/18 Functional Block Diagram
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4.2.1 T1 Pinout: CS61310 Shown
MCLK TCLK TPOS/TDATA TNEG/UBS MODE RNEG/BPV RPOS/RDATA RCLK XTALIN XTALOUT JASEL LOS TTIP TGND 28-pin PDIP MCLK TCLK TPOS/TDATA TNEG/UBS MODE RNEG/BPV RPOS/RDATA RCLK XTALIN XTALOUT JASEL LOS TTIP TGND 28-pin PLCC 28-pin PLCC
5 6 7 8 9 10 11 12 13 14 15 16 17 18 top view 4 3 2 1 28 27 26 25 24 23 22 21 20 19
TAOS/CLKE LLOOP/SCLK RLOOP/CS LBO2/SDO LBO1/SDI NLOOP/INT RGND RV+ RRING RTIP LATN NC TRING TV+
LXT310:
EGL
TAOS/CLKE LLOOP/SCLK RLOOP/CS LBO2/SDO LBO1/SDI NLOOP/INT RGND RV+ RRING RTIP LATN NC TRING TV+
LXT310:
EGL
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4.2.2 E1 Pinout: CS61318 Shown
MCLK TCLK TPOS/TDATA TNEG/UBS MODE RNEG/BPV RPOS/RDATA RCLK XTALIN XTALOUT JASEL LOS TTIP TGND 28-pin PDIP MCLK TCLK TPOS/TDATA TNEG/UBS MODE RNEG/BPV RPOS/RDATA RCLK XTALIN XTALOUT JASEL LOS TTIP TGND 28-pin PLCC
5 6 7 8 9 10 11 12 13 14 15 16 17 18 top view 4 3 2 1 28 27 26 25 24 23 22 21 20 19
TAOS/CLKE LLOOP/SCLK RLOOP/CS SDO SDI NLOOP/INT RGND RV+ RRING RTIP LATN NC TRING TV+
LXT318:
GND
TAOS/CLKE LLOOP/SCLK RLOOP/CS SDO SDI NLOOP/INT RGND RV+ RRING RTIP LATN NC TRING TV+
LXT318:
GND
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4.3 Clocking
The CS61310/18 do not require an external crystal to perform jitter attenuation. Therefore, if the devices are replacing an LXT310/318, the user has three options:
n n
Replace the pullable crystal required for the Level One circuit with a non-pullable crystal, or Use no crystal, so long as an external system clock is provided via MCLK.
n
Retain the pullable crystal required for the Level One circuit, thus making no changes,
Available Clock Sources
CS61310/CS61318 MCLK at 1X bit rate Drives Receiver and Jitter Attenuator through MCLK External crystal is ignored if transitions detected on MCLK
LXT310/LXT318 MCLK at 1X bit rate Drives Receiver through MCLK MCLK actively selected if XTALIN is grounded Jitter Attenuator actively disabled if XTALIN pulled up and XTALOUT left open (Note: JA not available if xtal not provided) N/A - Jitter Attenuator not available Transmitter driven through TCLK Crystal at 4X bit rate Pullable Drives Receiver and Jitter Attenuator through XTALIN, XTALOUT Drive TCLK from external source; can be connected to RCLK Use external clock to drive Receiver and Transmitter; crystal required to drive Jitter Attenuator
Reference provided by external source (through MCLK) only
Ground XTALIN to enable Jitter Attenuator Purity of external clock determines maximum performance of Jitter Attenuator Transmitter driven through TCLK Crystal at 4X bit rate Non-pullable
Reference provided by external crystal (through XTALIN/OUT) only
Drives Receiver and Jitter Attenuator through XTALIN, XTALOUT Drive TCLK from external source; can be connected to RCLK
References provided to both MCLK and XTALIN/OUT
Only MCLK will be used
Table 2. Clocking options for the Cirrus and Level One Long Haul LIUs
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4.4 Application Modes 4.4.1 Hardware mode
The following layout is a typical hardware-mode application for the CS61310/18.
+5V + 33 F RGND 28 Control & Monitor 1 26 27 12 23 11 5 7 6 Frame Format Encoder/ Decoder 8 3 4 2 9 10 TAOS
MCLK
0.1 F 21 RV+ 15 TV+
+
1.0 F TGND
RLOOP LLOOP LOS NLOOP JASEL MODE RPOS RNEG
RCLK
LBO1 LBO2
24 25
CS61310/ CS61318 IN HARDWARE MODE
RTIP
19 R1
1
2 RECEIVE LINE
RRING
20
5 1:1
R2
6
TPOS TNEG TCLK XTALIN XTALOUT RGND 22 TGND 14 TRING TTIP
16 13 R3
2 6 T2
1 TRANSMIT 5 LINE
Note 1: a 0.47F cap may be necessary on the receive side if common mode noise is an issue. Note 2: a 0.47F cap may be necessary on the transmit side to block DC saturation current through T2. Note 3: When replacing LXT310/318 with CS61310/ 318, the same crystal may be retained, it may be replaced with a non-pullable crystal, or it may be discarded so long as MCLK is present.
T1 100 R1() R2() R3() T2 100 9.1 9.1 1:2
E1 75 75 15 15 1:1.58
E1 120 120 15 15 1:2
Figure 2. Typical Hardware-Mode Application for the CS61310/18
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4.4.2 Host mode
The following layout is a typical host-mode application for the CS61310/18.
+5V + 33 F RGND 28 Control & Monitor 1 12 6 18 11 CLKE
MCLK
0.1 F 21 RV+ 15 TV+
+
1.0 F TGND
SCLK
CS
27 26 23 24 25 P Serial Port
LOS BPV LATN JASEL
INT
LBO1/SDI LBO2/SDO
RV+ 1 k 5 MODE 7 6 Frame Format Encoder/ Decoder 8 3 4 2 9 10 RPOS RNEG
RCLK
CS61310/ CS61318 IN HOST MODE
RTIP
19 R1
1
2 RECEIVE LINE
RRING
20
5 1:1
R2
6
TPOS TNEG TCLK XTALIN XTALOUT RGND 22 TGND 14
T1 100 100 9.1 9.1 1:2 E1 75 75 15 15 1:1.58 E1 120 120 15 15 1:2
TRING TTIP
16 13 R3
2 6 T2
1 TRANSMIT 5 LINE
Note 1: a 0.47F cap may be necessary on the receive side if common mode noise is an issue. Note 2: a 0.47F cap may be necessary on the transmit side to block DC saturation current through T2. Note 3: When replacing LXT310/318 with CS61310/ 318, the same crystal may be retained, it may be replaced with a non-pullable crystal, or it may be discarded so long as MCLK is present.
R1() R2() R3() T2
Figure 3. Typical Host-Mode Application for the CS61310/18
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4.5 Layout Comparisons 4.5.1 T1 Layout Comparison: CS61310 versus LXT310
The following partial schematics detail the minor difference in T1 layouts.
RTIP
19
100
1
2 RECEIVE LINE
RRING
CRYSTAL CS61310
20
5
1:1
6
9.1
TRING TTIP RGND 22 TGND 14
16 13 9.1
2 6
1:2
1 TRANSMIT 5 LINE
Notes: A 0.47F capacitor to ground may be necessary on the receive side if common mode noise is an issue. See the CS61310 data sheet. A 0.47F capacitor may be necessary in series with one of the transmit matching resistors to block DC saturation current. See the CS61310 data sheet.
RTIP
19
100
1
2 RECEIVE LINE
RRING
LEVEL ONE LXT310
20
5
1:1
6
TRING TTIP RGND 22 TGND 14
16 13
12.5
2 6
1 TRANSMIT 5 LINE
1:2
12.5
Figure 4. T1 Layout Comparison
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4.5.2 E1 Layout Comparison: CS61318 versus LXT318
The following partial schematics emphasize that there are no differences in E1 layout.
Note: E1 75 R1() T2 75 1:1.58 E1 120 120 1.2
RTIP
19
R1
1
2 RECEIVE LINE
RRING
CRYSTAL CS61318
20
5
1:1
6
15
TRING TTIP RGND 22 TGND 14
16 13 15
2 6
T2
1 TRANSMIT 5 LINE
Notes: A 0.47F capacitor to ground may be necessary on the receive side if common mode noise is an issue. See the CS61318 data sheet. A 0.47F capacitor may be necessary in series with one of the transmit matching resistors to block DC saturation current. See the CS61318 data sheet.
RTIP
19
R1
1
2 RECEIVE LINE
RRING
LEVEL ONE LXT318
20
5
1:1
6
TRING TTIP RGND 22 TGND 14
16 13
15
2 6
1 TRANSMIT 5 LINE
T2
15
Figure 5. E1 Layout Comparison
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4.6 Software Expansion: CS61310/18 shown
The register set of the CS61310/18 is shown below. The Level One equivalent devices provide only a register comparable to CR1 in the CS61310/18. If a user wishes to make use of the additional functionality of the Cirrus Logic devices, it is recommended that the system software be modified to accommodate the additional registers. A complete description of the registers, their functions, and the clock edges upon which serial data is valid may be found in the respective product data sheets.
5.2 Replacing LXT318 with CS61318
n n n n
Leave Pin 17 tied to GND, or disconnect Keep pullable crystal, replace with non-pullable, or remove Enable or disable jitter attenuator per Clocking table Implement additional software registers, as desired
6. CONCLUSION
It is extremely easy to replace the Level One Long Haul LIUs with the Cirrus equivalents. In doing so, users will gain additional functionality (should they wish to make use of it) and will reduce their BOM costs by eliminating the external crystal should they so desire. Design assistance is available from expert engineers at Cirrus Logic. For further information, please contact your local Cirrus representative, call 800-888-5016 or email tcomm@crystal.cirrus.com.
5. SUMMARY 5.1 Replacing LXT310 with CS61310
n n n n n
Replace 12.5 Transmit resistors with 9.1 Leave Pin 17 tied to GND, or disconnect Keep pullable crystal, replace with non-pullable, or remove Enable or disable jitter attenuator per Clocking table Implement additional software registers, as desired
7 6
LLOOP
5
RLOOP
4
LBO2a
3
LBO1b
2
CODER TAZ
1
NLOOP
0
LOS
ADDR 0x10 R/W 0x11 R/W 0x12 R 0x13 R/W 0x14
Control Register 1 (CR1) Control Register 2 (CR2) Equalizer Gain (EQGAIN) RAM Address (RAM) Reserved (Set to "0")
TAOS
AIS
RAMPLSE
RSVD = 0
LOOPDN
LOOPUP
RPWDN
TxHIZ
RSVD = 0
X
X
X
EQ4
EQ3
EQ2
EQ1
EQ0
MSB
-
-
-
-
-
-
LSB
0
0
0
0
0
0
0
0
Table 3. Control Registers of CS61310/61318 a.Bit 4 of CR1 is reserved (RSVD=0) on the CS61318. b.Bit 3of CR1 is reserved (RSVD=0) on the CS61318.
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* Notes *

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