Chapter 4: Serial Ports; Description; Mating Receptacles - Octagon Systems XE–700 Reference Manual

Chapter 4: Serial ports

Description

The XE–700 SBC has four serial ports, COM1 through COM4. COM1 is a dedicated
8-wire RS–232C. COM2 is a dedicated 4-wire RS–232C. COM3 and COM4 can be 4-
wire RS–232C, RS–422 or RS–485.
COM1 and COM2 are accessed at the 20-pin connector at J12. COM3 and COM4
are accessed at the 20-pin connector at J17 for RS–232C. COM3 and COM4 have
separate connectors for RS–422 or RS–485. Refer to the table on page 21 for which
connector to use for the various interfaces. Refer to the Cables section on page 22
for a description of cables that mate with these connectors.
These serial ports interface to serial device. All ports support 5-, 6-, 7-, or 8-bit
word lengths, 1, 1.5, or 2 stop bits, and baud rates up to 115.2K.
The serial ports have the following specifications:
16C550 compatible
16-byte FIFO buffers
IEC 1000, level 3, ESD protection
— Contact discharge ±6 kV
— Air–gap discharge ±8 kV
Backdrive protection
Up to 115.2k baud operation

Mating receptacles

Use a VTC–20F or VTC–20M cable to connect the 20-pin COM ports to external
serial equipment. The P2 and P3 connectors on these cables are DB–9 female
(VTC–20F) or DB–9 male (VTC–20M) connectors which plug directly into a 9-pin
serial cable. For RS-422 or RS-485 on COM3 or COM4, use a 0.100 inch RS422/485
Cable (part #6683).
Figure 4–1 (following page) shows serial devices connected to the XE–700 SBC. It
also shows the schematic for connecting RS–422 or RS–485 devices. Note that you
cannot use COM3 or COM4 for two different interfaces at the same time.
Figure 4–2 shows a null modem adapter connected to the COM1 port of a VTC–
20F. A null modem adapter is required when connecting a serial console.
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