Compaq Portable 286 Compaq Portable Computer, Compaq Plus Personal Computer, a - Page 120
Compaq Portable and Compaq Plus Asynchronous Communications/Clock Board, Jumper Settings
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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,