CM312 Datasheet, PDF (27/56 Pages) List of Unclassifed Manufacturers – Communications utilityModule

9
GND
GND
10
Facing the connector pins, the pinout is pictured in the following,
Table 10 Connector CN3 pin location in RS422/485 Mode
7
5
3
CTS-
CTS+
TXD-
RXD+
RXD-
TXD+
8
6
4
1
RTS-
RTS+
2
Notes on using RS422 or RS485 Modes
When using the serial port in RS422 or RS485 mode, the serial receiver is always enabled,
however the serial transmitter is enabled and disabled under software control in the following two ways.
By default, the transmitter is enabled by manipulating the Request To Send (RTS*) signal of the
serial port controller. This signal is controlled by writing bit 1 of the Modem Control Register (MCR) as
follows:
• If MCR bit 1 = 1, then RTS* = 0, and serial transmitter is disabled
• If MCR bit 1 = 0, then RTS* = 1, and serial transmitter is enabled
For more information on the serial port registers, including the MCR, please refer to a standard PC-AT
hardware reference for the 16C550 UART, or refer to RTDUSA application note ANC102 at
http://www.rtdusa.com
The other way to enable the serial transmitter is to write 1 to its corresponding bit of the
utilityModule’s internal common register 4, which sets the serial transmitter in “always on” mode. Please
refer to Internal Common Register Section for detail.
Second COM port, CN4
Please refer to the previous section on the first COM port CN3 for the description on CN4.
Third COM port, CN5
Please refer to the previous section on the first COM port CN3 for the description on CN5.
Fourth COM port, CN6
Please refer to the previous section on the first COM port CN3 for the description on CN6.
CM312 Quad Serial utilityModule
17
RTD Embedded Technologies, Inc.