>
> I am hoping somebody out there in PIC land may be able to help me.
> I am currently working on a simple home automation system using multiple
> 16C84's (max of 10) fitted with rs232 trancievers as slaves and a PC as
> the master controller. I am not sure how to go about connecting all the TXD
> lines on the slaves to the PC without causing possible conflicts. It is
> intended to be a multi-drop system with each slave having a unique node
> address and only responding when polled.

As it's clear from you discussion, RS-232 isn't designed for multidrop.
It's strictly a point to point protocol.

Best bet is to switch to RS485 transceivers. The 75176 from texas instruments
is an 8 pin 5V only chip that will allow up to 32 devices sharing the line.
Less than $2 US.

If you must stick with RS-232 then a wire OR configuration seems to be the
best bet. Put a diode in series with each Tx Line. Then the Tx line can only
drive current in a single direction. Then use a pullup resistor to tie the
line idle (-12V).

Note I've never tried this particular configuration, but assuming that
the pullup can keep within RS-232 slew specifications, it should work.

Best bet again is to go to RS-485. Check it out...

BAJ