Sending 0377 via KL8JA

Peter Coghlan cctalk at
Mon Jan 19 06:52:26 CST 2015

>I am noticing something odd in SimH when sending a 0377 (all ones)
>character. It seems to be duplicating the byte. I haven't read anything
>regarding this behavior. I'm away from my hardware PDP-8 at the moment, so
>I can't confirm that this is not the behavior that I would experience on
>the real thing.

It's not really that clear whether a telnet type connection is in use here but
could it be something that does telnet negotiation is sending data to something
which is not telnet negotiation aware?  0377 octal (FF hex) corresponds to
IAC which would get sent as IAC IAC.  Maybe monitoring the data on the network
would confirm?

>Run 'nc localhost 2222 | od -to1' in a terminal, then 'go 200' and
>repeatedly press 'c', seeing how many times it takes to generate a line of
>characters in 'od'. Then, 'd sr 0376' and confirm that it takes twice as
>many presses, indicating half as many characters being sent per TLS
>instruction with the latter.
>Can anyone else confirm this for me?

Sorry - I don't follow that at all and figuring it out is probably
above my pay grade :-)

Peter Coghlan.

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