16 Nov
2008
16 Nov
'08
2:10 p.m.
It looks like a converter box that takes TTL level
serial signals and
converts to RS232 levels, kind of like the MAXIM single chip solution
except that it is using 1488 and 1489 chips.
OK, such things did exist.
The problem is that it came with a PCjr, but it doesn't physically plug
into a PCjr. The onboard serial port is only 16 pins, while the
rectangular connector here is 20 pins. It physically doesn't work.
And the PCjr serial port is at RS232 levels anyway. The PCjr seiral cable
is just a cahle, no intenral componnets (I have the PCjr TechRef with
schematics...)
If it was used wit ha PCjr, then I would guess that the PCjr was
connected to the RS232 side of this coverter, and some other device,
using a TTL level serial port, was connected to the 20 pin header.
I can't think fo anything offhand that would have such a port. It might
have been something very specialised (say to control or program some
measuring instrument or something).
-tony