CM312 datasheet(27/56 Pages) ETC

27 / 56 page

CM312 Quad Serial utilityModule

RTD Embedded Technologies, Inc.

Facing the connector pins, the pinout is pictured in the following,

Table 10 Connector CN3 pin location in RS422/485 Mode

GND

CTS-

TXD-

RXD-

RTS-

GND

CTS+

RXD+

TXD+

RTS+

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 Datasheet(PDF) 27 Page - List of Unclassifed Manufacturers