Hatteland Display 20 inch - HM 20T07 MIL-H - Manual (Page 50)

50
Serial Communication (SCOM) Interface
Communication Interface
IND100084-7
Connectorization at unit
The unit provides two or one 9 pin D-shell with socket contacts (depending on model).
Pin assignments at the unit are as shown below.
Pin RS 232 RS422/ RS 485 full duplex RS 485 half duplex
1 +5V +5V +5V
2 Tx RxD- -
3 Rx TxD+ Data +
4 - GND GND
5 GND GND GND
6 - GND GND
7 - RxD+ -
8 - TxD- Data -
9 GND GND GND
For full duplex RS-485 , the receive and transmit pins can be altered at COM2. That is: Tx- at pin 2, Rx+ at pin 3, Tx+
at pin 7 and Rx- at pin 8. This can be done to simplify connections, as only one to one cables are needed throughout
an installation of several units. The alteration is selected by a slide switch on the Remote PCB labelled “one to one”
and “rx to tx”.