PET weirdness

From: Marko Mäkelä (
Date: 2001-10-31 14:17:55

Yesterday I ported the custom transfer routines of my cassette-to-RS232
adapter to the PET.  The first mistake that I made was a very stupid one:
I wasn't able to load the transfer program to the PET, because the tape
header identifier byte was 3 and not 1, the only code the PET appears to
accept for programs.  As the computer didn't display any "found" message
or anything, I was puzzled for a long time.

It was not too difficult to get the transfer going in cassette port #1.
But the second cassette port is more problematic, since the VIA clears the
status of CB2 (cassette #2 read) every time port B is read or written (and
cassette write is PB3).  Hmm, maybe I should misuse the data direction
register and use the pin as an open-collector output (acting either as a
constantly-zero output or as an input).  The microcontroller has internal
pull-up resistors.

Well, my actual question is: Why does the PET 8032 firmware contain the
start-up message both with the ### and the *** signs?  I thought that the
type of the message identified the BASIC ROM version.  (I noticed this
when I tested the transfer protocol by dumping the ROM.)


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