42
CMA34CR cpuModule
BDM-610000083
Rev L
Dual Serial Port Modes
The serial port connectors can be configured as dual serial ports in the BIOS. The mapping between the
connectors and COM port numbers is shown in Table 23. The supported combinations of serial port modes are
listed in Table 24, which also includes a reference to the corresponding connector pinout.
Table 23
Dual Serial Port Connections
Connector
COM A
COM B
CN7
COM 1
COM 3
CN8
COM 2
COM 4
Table 24
Dual Serial Port Modes
COM A
COM B
Pinout
Reference
Echo Mode
RS-232
RS-232
—
RS-422
RS-422
—
RS-485
RS-485
echo cancelled
RS-485
RS-485
with echo
1
1. Dual RS-485 mode with echo uses dual RS-422 mode pinout
WARNING
The dual serial port mode pinouts of the COM ports are
not
compatible with previous
generations of RTD cpuModules.
Note
The cpuModule has 120 Ohm termination resistors. Termination is usually necessary on all RS-422
receivers and at the ends of the RS-485 bus. Termination resistors can be enabled in the BIOS setup utility.
When termination is enabled in dual port mode, it is enabled for both ports.
Table 25
COM A (RS-232) and COM B (RS-232)
Pin
Signal
Function
In/Out
DB-9
1
DCD1
COM A - Data Carrier Detect
in
1
2
CTS1
COM A - Clear to Send
in
6
3
RXD1
COM A - Receive Data
in
2
4
TXD2
COM B - Transmit Data
out
7
5
TXD1
COM A - Transmit Data
out
3
6
RXD2
COM B - Receive Data
in
8
7
RTS1
COM A - Ready to Send
out
4
8
RI1
COM A - Ring Indicate
in
9
9,10
GND
Signal Ground
—
5
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