[Coco] The Trials to disable RS232 Status

[Barry Nelson]

> Darren A
> Sun Oct 1 11:44:13 EDT 2017
> 
> On Sun, Oct 1, 2017 at 2:19 AM, Arthur Flexser wrote:
> > Another method of bypassing the RS232 status check is these pokes:
> >
> > POKE &HFF23,&H30: POKE&HFF22,&HF9: POKE&HFF23, &H34
> >
> > This will work on any model CoCo, does not depend on what ROM version
> > exists in the machine, and does not require copying ROM to RAM.
> >
> > I works by using the PIA's data direction register to change the relevant
> > status bit in $FF22 from an input to an output, so that the RS232 status is
> > always seen as "ready" by Basic.
> 
> But wouldn't that be potentially damaging to the CoCo?  You are configuring
> the PIA pin to be an output driving the line low, while the SALT chip (or
> OpAmp) will be driving it high, essentially creating a short-circuit.
> 
> - Darren
According to the schematics I have for the CoCo 3 I would tend to agree with Darren that using those setting could be a bad idea. It looks like the SC77527 (U8) chip is wired directly to the 6821 (U4) with no resistors or other components in between.

I also found this hook which might be useful…

 $0170-$0172 Output to DEVN using PRINT (DOS SuperDosE6 JMP $c29c)

Perhaps by changing the address of this jump hook to your own routine you could do something...