Black Box LES401A, LES402A Appendix C RS-485 Connections, Appendix C. RS-485 Connections, Page

Appendix C: RS-485 Connections

Appendix C. RS-485 Connections

C.1 1-, 2-, or 4-Port Serial Server DB9 Pinout in RS-485H (Two-Wire, Half-Duplex) Mode

Figure C-1. DB9 male connector.

Table C-1. DB9 pinout in RS-485H mode.

RS-485 Signal Name	Direction	RS-485	DB9 M Pin
Data B (+)	In/Out	DATA B (+)	3
Data A (-)	In/Out	DATA A (-)	4
Signal Ground	—	GND	5

C.2 1-, 2-, or 4-Port Serial Server DB9 Pinout in RS-485F (Four-Wire, Full-Duplex) Mode

Figure C-2. DB9 male connector.

Table C-2. DB9 pinout in RS-485F mode.

RS-232 Signal Name	Direction	RS-422	DB9 M Pin
Receive Data A (-)	In	RXDA (-)	1
Receive Data B (+)	In	RXDB (+)	2
Transmit Data B (+)	Out	TXDB (+)	3
Transmit Data A (-)	Out	TXDA (-)	4
Signal Ground	—	GND	5
Clear To Send A (-)	In	CTSA (-)	6
Clear To Send B (+)	In	CTSB (+)	7
Request To Send B (+)	Out	RTSB (+)	8
Request To Send A (-)	Out	RTSA (-)	9

NOTE: Some RS-485 devices are marked opposite the RS-485 standard, which defines the Data B line as positive relative to Data A during a Mark state before enabling the transmitter, and after transmitting before tri-stating. If an RS-485 device does not respond, try swapping the Data B and Data A lines.

Page 58 724-746-5500 blackbox.com