jeevaaraam
Member level 2
I have faced peculiar problem with RS422 COMMUNICATION Rx side.
The circuit flow is add follows,
TX -> CABLE (Length 3m, twisted pair) -> 120 ohm shunt & Transceiver IC (Make - TI: AM26L, RS422 to TTL level) -> UART chip -> processor.
Note :
1) 120 ohm shunt & Transceiver IC are in Communication board.
2) UART chip & processor are in processor board.
3) The above two boards are connected through mother board.
4) Tx from ATE system.
Operated Baud rate: 115200 and 9600 ( Both case it was failed)
The setup should be worked upto 55 deg C.
The circuit is working fine upto 45 deg C. But it is not working above 45 deg C. If the board is cooled below 44 deg C, the test was passed.
The failure is found as two cases,
1. Data is missed (For ex: If Tx is AAFF, Rx is AFF)
2. CRC error.
I have probed the data at input (differential ) and output (single ended TTL) of Transceiver IC. The Tx data is available at all times. The time is observed as 8.04us at 115200 baud rate.
If the communication board is replaced by other one, the mentioned problem is not observed.
Hence , the problem is isolated to that particular communication board.
Since, the Tx data is available , while proving, I cannot isolated the issue in the particular board. Is it the PCB Malfunctioning above 45 deg C?
The circuit flow is add follows,
TX -> CABLE (Length 3m, twisted pair) -> 120 ohm shunt & Transceiver IC (Make - TI: AM26L, RS422 to TTL level) -> UART chip -> processor.
Note :
1) 120 ohm shunt & Transceiver IC are in Communication board.
2) UART chip & processor are in processor board.
3) The above two boards are connected through mother board.
4) Tx from ATE system.
Operated Baud rate: 115200 and 9600 ( Both case it was failed)
The setup should be worked upto 55 deg C.
The circuit is working fine upto 45 deg C. But it is not working above 45 deg C. If the board is cooled below 44 deg C, the test was passed.
The failure is found as two cases,
1. Data is missed (For ex: If Tx is AAFF, Rx is AFF)
2. CRC error.
I have probed the data at input (differential ) and output (single ended TTL) of Transceiver IC. The Tx data is available at all times. The time is observed as 8.04us at 115200 baud rate.
If the communication board is replaced by other one, the mentioned problem is not observed.
Hence , the problem is isolated to that particular communication board.
Since, the Tx data is available , while proving, I cannot isolated the issue in the particular board. Is it the PCB Malfunctioning above 45 deg C?