Black Box 1- Manual De Usuario
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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.
not respond, try swapping the Data B and Data A lines.