PXI8433/2: Jumper W1, enable 2-Wire-Auto mode permanently

[vobs]

Dear all,

I'd like to run the proprietary windows software PCM001Z on our PXI system. The software should communicate via one port of the PXI8433/2 RS485 card in two-wire-mode with a Toshiba frequency converter.

Unfortunately it seems as if the software clears the scratch register of the PXI8433 uart, what leads to disabling two wire mode.

My Questions:

* Is there a way to enable 2-wire-auto mode of the PXI8833/2 permanetly?  

* What is the use of the 5 jumpers marked "W1" on the PXI8833/2 board? Could these jumpers be used for configurating the PXI8433/2 card?

Thanks a lot in advance,

cheerio,

Volker.  

[vobs · Accepted solution]

Dear all,

meanwhile I managed to put port 1 of our PXI8433/2 card in 2-wire-auto mode w/o echo permanently by using a soldering iron 😉

The following steps were necessary:

1. To disable echo I simply connected the receiver enable pin /RE (3) of the RS422 line driver MAX3086 (U7) with the

      transmitter enable pin TE (4).

      Note: The /RE pin has to be unsoldered from the pcb.

2. 2-Wire-Auto mode is enabled permanently by connecting the Transmitter Enable of the above mentioned RS422 line

      drive to the TxRdy0 pin (21) of the OX16C954 UART (U11). Please note that the TE signal goes through the Digital

      Insulator ADuM1400 (U1). Therefore pin 6 of U1 has to be unsoldered from the pcb and connected to pin 21 of U11.

For correct RS485-2-wire-mode the following windows settings for port 1 must be set:

  [x] Use FIFO buffers

  Transmit Buffer: Low (1) -> put ruler to the leftmost border

  Transceiver Mode: 4 Wire