Acer G901 manual Serial port B jumpers

18 1 System tour

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	Pin	Jumper name - effect when shorted
block
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.