Specifications

Hardware Configuration
2–11
Figure 2–3 Serial 4 Interrupt Configuration (W5, W7)
When a serial port is disabled, leave its jumpers off to make its IRQ available to other peripherals
installed on the PC/104 expansion bus. For information about disabling the serial ports using SETUP,
see Chapter 3.
2.5.3 ROM-BIOS Installation of the Serial Ports
Normally, the ROM BIOS supports Serial 1 as the DOS COM1 device, Serial 2 as the DOS COM2
device, and so on. If you disable a serial port, and there is no substitute serial port in the system, then the
ROM-BIOS assigns the COMn designations in sequence as it finds the serial ports, starting from the
primary serial port and searching to the last one, Serial 4. Thus, for example, if Serial 1 and Serial 3 are
disabled, the ROM-BIOS assigns COM1 to Serial 2 and COM2 to Serial 4.
2.5.4 Serial Port Connectors (J11, J13)
Serial 1 and Serial 2 appear on connector J11; Serial 3 and Serial 4 appear on connector J13. Table 2-7
gives the connector pinout and signal definitions for J11 and J13. Both connectors are wired the same.
In addition, the table indicates the pins to which each signal must be wired for compatibility with DB25
and DB9 connectors. The serial port pinout is arranged so that you can use a flat ribbon cable between
the header and a standard DB9 connector. Split a 20-wire ribbon cable into two 10-wire sections, each
one going to a DB9 connector. Normally PC serial ports use male DB connectors. Table 2-8 shows the
manufacturer’s part number for mating connectors.