ard at p850ug1.demon.co.uk
Wed Jul 13 18:41:46 CDT 2005
> >>>>> "Jim" == Jim Beacon <jim at g1jbg.co.uk> writes:
> Jim> My 11/45 has a seperate "Paper Tape Advance" output on the
> Jim> console serial interface, whic is set by writing to a register -
> Jim> I assume that the Teleprint 390 / ASR33 has either a solenoid
> Jim> drive or a clutch that allows the tape to advance one character
> Jim> at a time, under processor control.
> Bit 0 in the receive control register, right? That's supposed to be
> the papertape reader "reader run" signal. It isn't used as a one
> character at a time thing; it is read/write and if set remains set
> until explicitly cleared.
Are you sure? I was under the impression that setting that bit
(conventionally done by INCing the appropriate location in the I/O page)
would turn on the reader run relay, which would then be turned off when
the card detected the start bit of the character. In other words it _is_
> The idea is that the system would accept interactive input by leaving
> this bit clear, but then when you told it to read a papertape it would
> set the bit. That starts the tape. The program would then see
> characters streaming in. At some point (perhaps when it sees a string
> of nulls, or when it knows the tape is finished by some internal
> coding) it would clear reader run again.
> I don't know if this actually was used much. The ASR33s I remember
> rarely if ever had this hooked up; the reader run control was done by
> flipping the papertape reader switch on the machine.
The reader run relay is not a standard Teletype fitment. It was a DEC
modification, Intel and others had similar modifications too (and
amazingly they werre all much the same). I believe, though, the Data
Dynamics 390 has a reader control relay as part of the call control unit
(which as I said is very different from the Teletype one).
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