
9.3.3
Operation
The SSCA includes six connection points for each of the six serial communication channels. The points include four signal
lines A-D, a signal return, and a shield common (SCOM).
Signal Assignments
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
The return for RS-232C is through the terminal called
Ret
. The signals for all six serial communication channels are arranged
in the same order, which is SCOM, A, B, C, D, Ret when viewed from left to right.
The groups of six signals for a serial channel are assigned to terminals adjacent to each other. When viewed from left to right,
the channels on the bottom set of terminals are 5, 4, and 1. The top set of terminals contain channels 6, 3, and 2 when viewed
from left to right. The board SCOM connections are grouped on the right side of the terminals. A signal location diagram is
included on the SSCA.
Terminal Board Screw Connections
Connection
Port 1
Port 2
Port 3
Port 4
Port 5
Port 6
SCOM
26
25
13
14
2
1
PT_A
28
27
15
16
4
3
PT_B
30
29
17
18
6
5
PT_C
32
31
19
20
8
7
PT_D
34
33
21
22
10
9
Ret
36
35
23
24
12
11
When using RS-422 or RS-485, a termination resistor must be provided at either end of a transmission line. The SSCA
provides selectable termination resistors for each pair of signal lines. Jumpers JP1A and JP1B apply or remove the
termination resistors between signals A-B and C-D. The same function is repeated for each serial communication channel.
The default jumper position includes a disconnected termination resistor. The SSCA is clearly marked to display the
relationship of the termination jumpers and the serial communication channel signals as displayed in the following figure.
Termination Jumpers
294
GEH-6855_Vol_II
GEH-6855_Vol_II Mark VIeS Functional Safety Systems Volume II
Public Information