Technical data

RS-422 Connections
Manual Documentation Number: Appendix B 75
Black Box Corporation - 1000 Park Drive - Lawrence, PA 15055-1018
www.blackbox.com -- Tech Support and Ordering: 724-746-5500 - Fax: [phone]
A
A
P
P
P
P
E
E
N
N
D
D
I
I
X
X
C
C
:
:
R
R
S
S
-
-
4
4
8
8
5
5
C
C
O
O
N
N
N
N
E
E
C
C
T
T
I
I
O
O
N
N
S
S
1, 2, or 4 Port Serial Server DB-9 Pin-out in RS-485H (two-wire,
half duplex) Mode
RS-485
Signal Name
Direction RS-485 DB9M
Pin
Data B (+) In/Out DATA B (+) 3
Data A (−) In/Out DATA A (−) 4
Signal Ground --- GND 5
Figure 53. DB-9 Pin-out in RS-485 Mode
RS-485 Connections
76 Appendix C Documentation Number: LES40xA-1105m
Black Box Corporation - 1000 Park Drive - Lawrence, PA 15055-1018
www.blackbox.com -- Tech Support and Ordering: 724-746-5500 - Fax: [phone]
1, 2, or 4 Port Serial Server DB-9 Pin-out in RS-485F (four-wire, full
duplex) Mode
RS-422
Signal Name Direction RS-422
DB9M
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
Figure 54. RS-422 Connections in a DB-9 Connector
N
N
o
o
t
t
e
e
:
:
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.