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Problem: GMaster RS485 is always half-duplex

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akidder

1519 Posts

Posted - 05 Mar 2003 : 11:26:08

Q: No matter how I set JP8 and JP11, GMaster RS485 is always half-duplex.
Q: RS-485 TX and RX are always shorted together.

We've identified that some Graphics Master development systems were shipped with two resistors populated that force RS-485 to half duplex. These resistors normally are used in production systems to eliminate the shunts placed at position 1-2 of JP8 and JP11.

If your application requires full-duplex RS-422/485 operation, please take a look at the following steps to determine if this is the source of the problem you are experiencing:

To determine if your system requires rework...

1. This issue applies only to revision C Graphics Master boards. Confirm you have revision C by locating the "170110-9000C" etched in the copper on the underside of the board.

2. Determine if the resistors are populated on the board. R242 and R243 are on the underside of the board, near Serial 3 connector J10 under boot ROM U22. The following image pinpoints their location:

If your system requires rework...
If your development system has either of these resistors populated, you can choose to do the rework yourself or return the systems to ADS for rework:
1. For organizations that have SMT rework stations, you can remove the resistors yourself. (Please use personnel certified in SMT rework. ADS does not warranty damage to the circuit board caused during rework.)
2. Otherwise, contact us to return your Graphics Master for repair at your convenience.

Drew Kidder
ADS Technology Transfer

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