Acer Altos G900, User Manual

Page: 34 / 248

1 System tour 18
Serial port B jumpers
The table identifies the function of each pin pair on the serial port B
jumper block (JP25). By default, the serial port B connector is an RJ-45,
which has only eight pins and doesn't provide separate DCD and DSR
signals. The serial port B jumpers let you configure the DSR and DCD
signals passed from the port connector to the inputs of the UART. The
default configuration has jumpers installed on pins 1 and 2 and on pins
3 and 4.
Caution! Never install jumpers on pins 3 and 4 and on pins 5 and
6 at the same time. This would cause both the DCD and DSR
signals from the connector to drive the DCD input on the UART,
resulting in signal contention.
Jumper
block
Pin Jumper name - effect when shorted
JP25 1-2 DSR to DSR - DSR from connector is passed to DSR
input on UART (RJ-45 & DB9).
3-4 DSR to DCD - DSR from connector is passed to DCD
input on UART (RJ-45 only).
5-6 DCD to DCD - DCD from connector is passed to DCD
input on UART (DB9 only).
7-8 Spare.
AA G900 ug - EN.book Page 18 Wednesday, September 25, 2002 5:23 PM