In RS-232C systems, it is often not desirable to have a hard ground of the Ret signal path on both ends of a cable. The SSCA
includes jumper selectable grounding options for each of the six Ret lines. The line may be grounded through a 100 Ω resistor
or through a 0.01 uF capacitor / 1M Ω resistor parallel combination. If the device attached to the SSCA has a hard ground of
the Ret line, the capacitive ground should be selected on the SSCA. If there is not a hard ground on the connected equipment,
the resistive ground (default position) should be selected on the SSCA.
Ret ground jumpers are identified on the SSCA as JP1R through JP6R. Positions are displayed as resistive (RES) and
capacitive (CAP) return connection. All jumpers are clearly labeled.
Ground Jumpers
9.3.4
Specifications
Item
SSCA Specification
Number of Channels
6
Termination Resistors
Jumper selectable between open and resistor of 121 Ω
RS-232C Return Path Ground
Selectable between resistive ground of 100 Ω, ½ W, 1% or
1M Ω, ½ W, 1% in parallel with 0.01 uF, 500 V, 10% capacitor
Max Drops in RS-485 Systems
8
Size
15.9 cm high x 10.2 cm wide (6.25 in x 4.0 in)
Technology
Surface-mount
9.3.5
Diagnostics
The JA connector on the terminal board has its own ID device that is interrogated by the I/O pack. The ID device is a
read-only chip coded with the terminal board serial number, board type, revision number, and J connector location. When this
chip is read by the I/O processor and a mismatch is encountered, a hardware incompatibility fault is generated.
PSCA Modbus Master (Serial Communication) Module
GEH-6855_Vol_II System Guide 295
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