Sending 0377 via KL8JA

Kyle Owen kylevowen at
Sun Jan 18 23:39:49 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.

Here's how I reproduced it:

        CLA OSR
        JMS SEND
        JMP 200
SEND,   0
        JMP .-1
        JMP I SEND

at ttix 2222
set ttox0 8b
load test.bin
br 200
d sr 0377

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?



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