14 Jun
2015
14 Jun
'15
10:24 p.m.
The rear DB25 serial connector is an A & B serial
port combined.
Sun had/sold a special Y-splitter cable to use for the combined port.
The RS232 specification allows for 2 serial channels on the DB25 connector. Most
machines only use the primary channel. and Sun were sensible enough to wire their
'2 ports on one connector' so that port A uses the primary channel pins and port
B
uses the 'back channel'. This means that if you plug a normal, minimally-wired
serial cable in (say an adapter to a PC DE9 port) you connect to port A. You only
need the splitter cable if you want to use port B
-tony