In article <1992Sep7.215917.1349@news.iastate.edu> jnelson@iastate.edu (Jeremy F Nelson) writes:
> You might remember my flame of supra's rs232 interface. However, i have gotten my hands on a few other rs232 interfaces and they have all failed.
> I have tried all of these on an SX-64 and an old c=64
>
> Interface sx-64 old c-64
>
> Supra Peak Modem Interface No response No response
> Aprotek RS232 Interface *** No response
> 'deluxe RS232 Interface' No response No response
> (company not known)
> *** computer failed to complete bootup when turned on.
>
>I had someone check the RS232 interfaces on both of these machines, and they appear to be ok coming from the computer, but dead coming out of the interface.
>Also, the signal coming out of the ISN port in the wall is also OK.
Just a note. Some RS-232 interfaces will always fail on an SX-64.
It's because the 9VAC lines coming out of the user port on the SX-64 are
not equivalent, circuit-wise, to a regular C-64 user port.
I built my own RS-232 port from an old schematic in Compute!. It works
fine on a regular C-64 and Vic-20. No go on the SX-64. It received
data just fine, but wouldn't transmit. The problem was that it wasn't
doing the -12v/+12v swing needed for RS-232 (it was more like 0v/+24v).
