Vecow MTC-2021, User Manual

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13 GETTING TO KNOW YOUR MTC-2021
2.2.12 Serial Port COM 3/ COM 4
COM 3 and COM 4 can be configured for RS-232, RS-422, or RS-485 with auto
flow control communication. Serial Port 2 default setting is RS-232, if you want
to use RS-422 or RS-485, you can find the setting in BIOS.
3 4
Serial
Port
Pin No. RS-232 RS-422
(5-wire)
RS-422
(9-wire)
RS-485
(3-wire)
3,4
1 DCD TXD- TXD- DATA-
2 RXD TXD+ TXD+ DATA+
3 TXD RXD+ RXD+ -----------
4 DTR RXD- RXD- -----------
5 GND GND GND GND
6 DSR ----------- RTS- -----------
7 RTS ----------- RTS+ -----------
8 CTS ----------- CTS+ -----------
9 RI ----------- CTS- -----------
The pin assignments are listed in the table as follow :
BIOS Setting Function
COM 3 / COM 4
RS-232
RS-422 (5-wire)
RS-422 (9-wire)
RS-485
RS-485 w/z auto-flow control