[Coco] Test RS232 pak

[Darren A]

On 3/31/09, Bill wrote:
> I was given an RS232 pak, and the one who gave it to me said he thought it
> MIGHT be bad.
>
> How can I test to be sure? I've done an EXEC 49152 and come up with the
> "Deluxe RS-232 Program Pak" screen. It gives me several choices, B (Baud
> rate), D (Duplex), W (Word length), P (Parity), S (Stop bits), L (Auto line
> feed), U (Upper case only), M (Modem 1), and Z (Terminal Communications
> mode).
>
> Regardless of which key I press, nothing changes, and nothing happens when I
> hit the <BREAK> key (it doesn't "Break from Menu")
>

Even pressing the 'Z' key does not change the menu option?  That's
quite strange since it has nothing to do with the functioning of ACIA
chip. It almost sounds like the ROM is defective, which would be very
unusual.

Make sure the edge connector contacts are clean and maybe re-seat the
socketed chips. Also try entering POKE 65315,52  before doing the EXEC
49152 and see if it makes any difference.

If you have a meter you can test for voltage levels on the DB25
connector.  The simplest test is to probe GND (pin 7) and DTR (pin
20).  This should show a negative voltage at power on / reset.
Entering POKE 65386,1 should change it to a positive voltage and POKE
65386,0 return it to negative again.

If you're doing this with a CoCo 3 you may have the power supply issue
with the serial pak that others here have mentioned before.

Darren