Ampro Corporation LITTLE BOARD P5X - Manual (Page 34)

2–16
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.
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– 11 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– 12 shows the manufacturer’s part number for mating connectors.