[GreenKeys] Model 15 + C-64 Baud rate question

[drlegendre .]

Jeff,

On Sun, Jul 5, 2015 at 11:05 AM, Jeffrey D Angus <jdangus at att.net> wrote:

> The C64 does not have a serial port as such. It does have a serial buss,
> for that was for communicating with the printer, disk drives, cassette
> etc.
>
> "External" communication was done via the cartridge edge connector
> on the back.


The RS-232 serial 'port' on the C-64 is entirely separate from the CBM /
IEC serial buss used to connect disk drives and printers.

CBM logical device ID 2 is RS-232 via the +user+ port. It's handled like
any other logical device from BASIC, or via KERNAL routines from ML. From
what I understand, it's a fairly standard RS-232 implementation, but it
uses TTL logic levels rather than the +/-9V of the RS-232 spec. A MAX232
chip is all that's required to correct the voltage level issue.

I built up an adapter for it two nights ago, but the chip is having an
overheating problem. Something to do with missing pull-up resistors on the
TTL inputs, I've read.
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