27 Nov
2003
27 Nov
'03
1:49 a.m.
Some place in the pdp-8E/M docs there must be specs
for the TTY and
reader control circuits. Take a look at the TTY I/O prints and see
what devices DEC used to drive the relay circuit.
The circuit used in e/m machines appears to be overkill -- it can drive
100ma, and kinda had me worried. I rechecked the circuit used in the 8L,
and it looks set up for about 30ma. I can do that without too much trouble.
If I can't find a TTY to test with, I'll just spec the resister value for
30ma and hope it works out :-).
Vince