Specifications
Analog Input Modules
126
31007715 6/2008
Status
Byte Structure
The second and fourth STB ACI 1230 registers in the input block of the process
image are the status words. The STB ACI 1230 can detect and report current
overflow conditions.
The six LSBs in each register represent the status of each input channel:
1 Bit 0 represents global status (GS). It has a value of 0 when no errors have been detected.
It has a value of 1 when bit 1 and/or bit 3 has a value of 1.
2 Bit 1 represents the status of PDM voltage on the island’s sensor bus. It has a value of 0
when no PDM voltage errors are detected. It has a value of 1 if sensor power has been
shorted. A PDM short turns on the GS bit (bit 0).
3 Bit 2 represents the presence or absence of an OCW. It has a value of 0 when the current
is less than or equal to 20 mA. It has a value of 1 when the current is greater than 20 mA.
An OCW in the STB ACI 1230 does not turn on the GS bit (bit 0).
4 Bit 3 represents the presence or absence of an OCE. It has a value of 0 when the current
is less than 20.48 mA and a value of 1 when the current is greater than or equal to
20.48 mA. An OCE in the STB ACI 1230 turns on the GS bit (bit 0).
5 Bit 4 represents the presence or absence of a UCW. It has a value of 0 when the current
is greater than or equal to 0.48 mA and a value of 1 when the current is less than 0.48 mA.
A UCW in the STB ACI 1230 does not turn on the GS bit (bit 0).
6 Bit 5 represents the presence or absence of a UCE. It has a value of 0 when the current is
greater than 0 mA and a value of 1 when the current is less than or equal to 0 mA. A UCE
in the STB ACI 1230 does not turn on the GS bit (bit 0).
Note: The detection of error conditions on the PDM input power connection may
be delayed by as much as 15 ms from the event, depending on the sensor bus
load, the system configuration and the nature of the fault.
Field power faults that are local to the input module are reported immediately.
STB ACI 1230 Status Register Format
always set to 0
67
1
23
4
5
0
1415
9
10
11
1213
8
not used;
GS (see 1)
PDM (see 2)
OCW (see 3)
OCE (see 4)
UCW (see 5)
UCE (see 6)
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