9.3.6.3
RS-422
•
There is the need to provide a termination resistor at either end of a transmission line.
•
SSCA provides selectable termination resistors for each pair of signal lines.
•
Jumpers JP#A and JP#B apply or remove the termination resistors between signals A-B and C-D.
•
Above Point 3 function is repeated for each serial communication channel. The default jumper position is to disconnect
the termination resistor.
•
The SSCA is clearly marked to display the relationship of the termination jumpers and the serial communication channel
signals.
The configuration at SSCA jumper
(JP#A, JP#B set to IN)
must match the ToolboxST configuration as displayed in the
following diagram. The 120 Ω resistance selection is used as an example.
Terminal Board Screw Connections
Channel
SCOM
A
B
C
D
RET
Channel 1
26
28
30
32
34
36
Channel 2
25
27
29
31
33
35
Channel 3
13
15
17
19
21
23
Channel 4
14
16
18
20
22
24
Channel 5
02
04
06
08
10
12
Channel 6
01
03
05
07
09
11
Protocol
A
B
C
D
Cable Length
RS-422
TX+
TX-
RX+
RX-
Up to 305 m (1000 ft)
RS-485
TX/RX+
TX/RX-
Jumper from A
Jumper from B
Up to 305 m (1000 ft)
RS-232C
DTR/RTS
TX
CTS
RX
Up to 15 m (50 ft) or 2500 pF
298
GEH-6855_Vol_II
GEH-6855_Vol_II Mark VIeS Functional Safety Systems Volume II
Public Information