Octagon XE-900, Reference Manual

Page: 41 / 122

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Chapter 4: Serial ports
Description
The XE–900 SBC has six serial ports, COM1 through COM6. COM1 is a dedicated
8-wire RS–232C. COM2, COM3, and COM4 are dedicated 4-wire RS–232C. COM5
can be 4-wire RS–232C, RS–422, RS–485, or TTL. COM6 can be 4-wire RS–422,
RS–485, or TTL.
COM1 and COM2 are accessed at the 20-pin connector at J13. COM3 and COM4
are accessed at the 20-pin connector at J15. COM5 and COM6 have separate
connectors for the supported interfaces. Refer to the table on page 22 for which
connector to use for the various interfaces. Refer to the
Custom Cables section on
page 23 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. Use a VTC–9F or VTC–9M to connect the 10-pin COM5 RS–232C port
to external serial equipment For RS-422 or RS-485 on COM5 or COM6, use a 0.100
inch RS422/485 Cable (part #6683).
Figure 4–1 (following page) shows serial devices connected to the XE–900 SBC. It
also shows the schematic for connecting RS–422, RS–485 and TTL devices. Note
that you cannot use COM5 or COM6 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.
Serial port configurations
COM1 and COM2 are always enabled. COM3-6 can be configured in Setup in the
Custom Configuration menu. The selections are Normal, Alternate, and Disabled.
Normal and Alternate select different addresses for COM5 and COM6. See Table
4–1 on page 43. You must also select the Mode for COM5 and COM6. For RS–232C,
RS–422 or TTL select RS232/422. For RS–485 select RS485. For additional