At 14:14 3/10/98 -0500, you wrote:
>Does anyone know off-hand the memory address and value for setting the RS232
>TX line high on a PC? I need to trigger a relay connected to this line.
>
>Thanks.
>
>C. Webb

Hi,
First of all, what do you mean HIGH on TX line on RS232 port of PC ?
The TX and RX lines (in RS232) are not on TTL level.
The 'logic 1' on TX (idle state) means this line is about -12V respect
to ground, the 'logic 0' on TX (mark state) means this line is about +12V
respect to ground.
Apart from this, you can't change the state of TX in this way (to control
relay).
Instead of TX, use the RTS or DTR signal.
These signals are TTLs, and it is easy to use as general purpose bits.
To change these signals, set or clear the appropriate bit:
(DTR)
[baseaddr+4].0 (ie. base address of serial port, eg. com1=0x3f8,
so the appropriate bit is the lsb of 0x3fc)
(RTS)
[baseaddr+4].1 (ie. base address of serial port, eg. com1=0x3f8,
so the appropriate bit is the second bit of 0x3fc)

bye
csaba