16 Apr
2003
16 Apr
'03
3:28 p.m.
OK now the light has finally come on. Thanks to all who provided
different pieces of the puzzle. I had assumed that the PDP-8
turned on the reader, read in however many words from the tape
reader it wanted, and then shut it off. It never occurred to me
that DEC would toggle this line on every character read, let alone
hard-wire this function, given the very slow speed of the tape
compared to even a PDP-8! I suppose I could have figured this out
by looking at the M706 schematic though...
So I'll put a relay in my ASR33 but I'm don't think I'll wire the
power switch connections, just the reader magnet path. I wouldn't
be using the 8/L and TTY without both being turned on anyway, and
only an SPST contact will be required.
-Charles
From: Ethan Dicks <erd_6502(a)yahoo.com>
The KCC IOT (6032) clears the Reader Run flip-flop that
drives
the buffer that activates the relay.
When the code running on the PDP-8 tells the console
hardware to read a
byte from the console, the normal sequence of IOTs toggles the bit without
any extra programming required.