--- Tony Duell <ard_at_p850ug1.demon.co.uk> wrote:
> What I/O port? The games port? There was rumoured to be a bit-banging
> routine to output serial data on one of the outputs there. But I never
> heard of it being in a PROM.
I don't know where my friend got it, but we rigged up a bit-banging-serial-
port between the joystick port of an Apple II and the User Port of a C-64
to transfer the data portion of an Infocom game from an Apple disk to a
C-64 disk (it all worked once we figured out the sector mapping).
> The bit-banging serial port is a pretty simple device. Single-bit in and
> out buffered to RS232 and current loop levels. And a program to shift
> data in and out in software.
We didn't even have level shifters - TTL on both sides, but RS-232 _is_
the more typical use.
> Believe me, after you've tried to use this card seriously you (a) wish
> for a real serial card with a 6850 or 6551 on it and (b) want to do
> unprintable things to the designers...
The C-64 comes with 1200-baud bit-banging in ROM. That's why we did it
that way. UARTS are much nicer (having later aquired a Super Serial Card),
but not all micros had them.
-ethan
=====
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Received on Thu Aug 24 2000 - 11:14:28 BST