[Coco] Bit Banger Port Signals

[Darren A]

On Sat, Mar 30, 2013 at 2:30 PM, Gary Becker wrote:
>
> I had a question about how the Bit Banger Serial port is being used. The three signals are labeled in the service manual as RS232C OUT, RS232C IN, and CD. How are people using the CD pin? If it was hooked up to a modem, the CD pin would indicate a connection was made by the modem. But since modems are not used much any more, does this pin really make sense? I thought using it for a CTS would make more sense. Is anyone using it for this function? Is anyone using it at all?
>

The pin labeled CD can be used to generate an FIRQ interrupt through
one of the PIAs.  I've never used any modem-based software on the
CoCo, so I have no idea if it's actually used for CD.

The only software I am aware of that relies on that pin is the 230
kbps bit banger client for DriveWire.  To achieve that speed, the
RS232C IN and CD are tied together. This allows the software to use a
SYNC instruction to align with the leading edge of a start bit.

Darren