DEC VT05 with OS/8 -- basic system rebuild?
bqt at softjar.se
Mon May 18 13:15:35 CDT 2009
Rick Murphy <rick at rickmurphy.net> wrote:
> At 05:17 AM 5/17/2009, Johnny Billquist wrote:
>> Chris Elmquist <chrise at pobox.com> wrote:
>>> I may have missed some facts earlier in this thread-- but does the
>>> obey hardware flow control such as CTS? ie, if CTS is low, will it be
>>> blocked from transmitting? If that is obeyed by all of your OS and
>>> software, then it is not hard to build a microcontroller that would sit
>>> between the system and the terminal, adding the delays you need on <cr>
>>> while buffering for and hardware flow controlling back toward the PDP-8.
>> In general, when talking about DEC equipment, the answer to that
>> question is *always* no, for the simple fact that DEC didn't do
>> hardware flow control. Hardware flow control is actually against the
>> RS-232 spec, and DEC didn't abuse standards (unlike most other companies).
> And, of course, there's a pretty good chance that this VT05 is
> connected via 20ma, not RS232.
> (Assumption based on the fact that there's an easy fix in the KL8-JA;
> given that this hasn't been used to fix the problem, it's probably not
> an omnibus computer. Pre-8/E serial devices were often current loop.)
Assumption wrong. :-)
The original posted have a KL8-E, which is software compatible with the
KL8-JA, but don't have the filler fix that the KL8-JA have.
They are both omnibus devices.
The KL8-E is actually kindof cool, since it implements a UART in
discrete logic. One side effect of that implementation is that you can
send a break character, since the transmit shift register is always
loaded immideately, even is a character is currently being transmitted,
and the stop bit is also shifted through the register, thus you can
"overwrite" the stop bit with additional data.
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
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