Chapter 8.8 Compaq Portable and Compaq Plus Asynchronous Communications/Clock Board
Jumper Settings
Jumpers on the COMPAQ Portable and COMPAQ PLUS asynchronous communications/
clock board determine the communications address and the interrupt selection
on the board.
Device U13 allows the selection of a 20 mA current loop
operation rather than the standard RS-232-C voltage operation.
DO NOT attempt to install two asynchronous communications/clock boards in one
system.
If two boards are installed, incorrect operation will result.
For locations of the COMPAQ Portable and COMPAQ PLUS asynchronous
communications/clock board jumper settings, see Figure 8.8-1.
See Table 8.8 for jumper setting information for the asynchronous
communications/clock board.
Table 8.8.
COMPAQ Portable and COMPAQ PLUS Asynchronous Communications/Clock
Board Jumper Settings
==============================================================================
Jumper
Location
Function
Pin 1 to Pin 2
Pin 2 to Pin 3
------------------------------------------------------------------------------
J702
COM1/COM2 select
COM2 Address
COM1 Address
(default setting)
------------------------------------------------------------------------------
J703
Interrupt select
IRQ3
IRQ4 (default setting)
------------------------------------------------------------------------------
U13
Current or voltage
Pins 5-12, 6-11,
operation
7-10,8-9:
(shunt module)
Serial RS-232-C
operation
Pins 1-16, 2-15,
