[Coco] Re: archive posted - PC<->CoCo RS232 info

[John E. Malmberg]

Robert Emery wrote:
> A while back Paul DeMarni took down his web page and asked someone to save and
> maintain the information. I saved what I could and have finally got it all
> updated and posted to my geocities account. Here's the link:
> 
> http://www.geocities.com/theother_bob/PaulDpages/index.html

I have a problem with the information on the pages, as the COCO bit 
banger port has 3 signal lines and a ground.

It has a read data, xmit data, DCD/CTS/DSR connection and a signal ground.

The ROM routines require a the signal line DCD/CTS/DSR line to be 
asserted, or they would only output one character, and the internal 
DLOAD command reads off of the read signal.

The only way a three wire cable would work for bi-directional 
communications is either with non-ROM routines on the COCO side, and 
looks like it would require the connection to be half duplex.

It looks like it should also be incompatible with the serial driver for 
the bit-banger in stock OS-9.

Of course the bit-banging software as written in the ROMS is effectively 
a half duplex operation.  An assembly language programmer could possibly 
work out a full duplex operation.

I would have to dig up my COCO documentation to see what line has been 
left off.  My guess is that these arrangements are using the DCD/CTS/DSR 
line as the received data line.

-John
wb8tyw(at)qsl.net
Personal Opinion Only