Product Reference
2–13
ROM-BIOS Installation of the Serial Ports
The ROM BIOS normally supports Serial 1 as the DO S CO M1 dev ice, Serial 2 as the D OS CO M2
device, and so on. If a serial port is disabled and there is no subst itute se rial port in the sy stem, the
ROM-BIOS assigns the COM designation s a s it fin ds the seri al por ts, star ting f rom the pri mary
serial port and searching to the last one. For example, if Serial 1 is disabled, the ROM-BIOS
assigns COM1 to Serial 2 (unless another Seri al 1 i s disco ver ed). Th e ROM B IOS scan s I/O
addresses for serial ports in the following ord er: 3F 8h, 2F8h, 3E8h , and 2E8h.
Serial Port Connectors (J11, J13)
Serial 1 and Serial 2 appears on connector J11. Ser ial 3 and Ser ial 4 appear o n conn ector J13. Bo th
connectors are wired the same, J11 for serial 1 and 2, and J13 fo r seria l 3 an d 4. Table 2–8 de tai ls
the connector pinout and signal definitions for both ports. The table also identifies the pin numbers
where each signal must be wired for compatibility with standard DB25 and DB9 connectors. A flat
ribbon cable connects the header to a standard DB9 connector.
Note
PC serial ports are typically equipped with male DB9 connectors.