Wouter van Wyk wrote:
> Hi
>
> I am using the TS-ISO485 RS485 driver card with my TS-7250. Is anybody
> using this card in half-duplex mode? I am having problems receiving
> data in this mode (TX is fine). The problem is that the RS-485 driver
> chip used for TX/RX in half-duplex mode always has it’s DE/!RE high
> (measured it with a scope) – in other words it is configured as a
> driver. These pins on the driver are controlled by the TX_ENA output
> signal of a CPLD connected to the UART (16C550). There is a number of
> modem control lines (RTS, CTS, DTR, DSR, OUT1, OUT2, etc.) connected
> between the UART and CPLD. I need to know what the state of these
> modem control lines should be in order to drive the TX_ENA output on
> the CPLD low. I have tried a number of combinations, but with no luck.
>
> My test application is very simple: open the device, configure the
> driver and then do a read().
>
> If I reboot the TS-7250 (and before I start my app), the TX_ENA signal
> is low and I can see data being received on the RX pin of the RS-485
> driver. As soon as I start my application the TX_ENA signal goes high
> and no data is received on the RX pin.
>
> Any suggestions will be appreciated.
>
> Thanks
>
> Wouter
>
>
something is not right i quizzed tech support pretty hard on 485 half
duplex and direction control
and was told the cpld contains a register that counts out going bits and
then waits for the last bit
to complete and then automaticaly switches back to rx mode, tx is supose
to be triggered by a load
of the uart. Note i have not tried this yet but will be doing so shortly.
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