I haven't tried it, but...

        Since DB25-17 is low to "select" the printer, can we just set
this pin low when we want to talk to the printer and set it high when we
want to talk to an attached PIC?  The PIC would tristate all its lines
and ignore data when -Select is low, then go "on the bus" when -select is
high.  Do we already have an "address" line to select between a printer
and a dongle?  Would some re-initializatin of the printer be required
after "selecting" it?

Harold