19 Nov
2005
19 Nov
'05
2:27 a.m.
Today I was hooking up my homebrewed driver board to the M-series
connector on the back of my Tally 420PR tape punch (interfaces to
my 8/A and . Fortunately, before I inserted the eight data pins
into the connector body it occurred to me that Tally and DEC might
not interpret the holes in the same order. And indeed they don't!
The paper tape has five holes on one side of the sprocket hole and
three on the other. Typical DEC terminology is Bit 1 = MSB and Bit
8 = LSB. Is that in fact how DEC labeled it?
Err, that depends on the DEC machine. My PDP11 has bit 0 as the LSB and
bit 15 asn the MSB. The PDP8/e on my desk has bit 0 as the MSB and bit
11 as the LSB . I don't know of any DEC machine that has bit 1 as the MSB
Is the MSB on the outside of the 5-hole side or the 3-hole side?
Which hole on the tape is which?
MSB LSB
7 6 5 4 3 * 2 1 0
Even more interestingly, Tally labels their punch pins as follows:
(* is the sprocket hole)
8 7 6 1 2 * 3 4 5
I have an idea that gets 1...5 right for 5-level baudot tape...
-tony