IBM didnb't have a cable for the 5150 cassette
port!
But it used the RS TRS80 cable.
Hnady, that ;-)
Since they used the same connector and pinout, can we assume that they
were identical in signals as well :-?
Well, the hardware signals are the same apart form the fact that on the
5150 there's a jumper on the motehrboard that sets the output level (PC
to recorder signal). BAsically the 2 positions give microphone or line
(aux) level.
I am not sure about the data encoding. It's in the TechRef, which I'll
dig out another time if nobody else has it. I am prrry sure the PCjr
encoding is the same as the 5150, but the connector is different (as
you'd expect on the PCjr).
IIRC, for laoding, the PC did the data decoding entirely in software.
For saving, the signal was generated by one of the timers in the 8253
with a lot of softare support.
-tony