is the tu58 basically a serial device?
Generally, yes. The serial port can be configured to be RS232 or RS422
IIRC by some jumpers on the board. There's another jumper to set the baud
rate. At the bit level it uses the normal asynchronous protocol (like
most common serial ports), the format of the command packets, etc is
given in the manual
The reason I say 'gnerally serial' is that the printset I have for the
TU58 also gives schematics for a parallel version. I've never seen this
one, though. The TU58 in my 11/730 CPU is certainly the standard serial
version (even though the 2 drives and the controller card are physically
arranged somewhat strangely)
-tony