Rockwell Automation T7408 ICS Regent+Plus DC Digital Input Modules 24VDC, 48VDC and 120VDC - Manual (Page 10)

DC Digital Input Modules (T7401, 02, and 08)
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I n d u s t r i a l C o n t r o l S e r v i c e s
Figure 8. Programming Fault Tolerant Digital Inputs.
In this illustration, VOTE_A_NAME, VOTE_B_NAME, and
VOTE_C_NAME represent the three digital inputs to be two-
out-of-three voted. ERROR_A_NAME, ERROR_B_NAME
and ERROR_C_NAME are the error bits for the digital
inputs. RESULT_NAME is the result of the voter instruction.
The field Msec is the time, in milliseconds, an input can be
incorrect before signaling an error. RESET_NAME is the
reset bit used to reset the latched error bits.
The voter instruction can be used to vote digital input points
or entire digital input modules. When voting digital input
modules, the tag names VOTE_A_NAME, VOTE_B_NAME,
and VOTE_C_NAME would be the names of the digital input
modules and RESULT_NAME would be a shared variable
register. After voting the modules, a block move instruction
should be used to move the contents of the register
RESULT_NAME into individual shared variable control
relays. Refer to the W
INTERPRET Help files for more
information about the block move instruction and shared
variable definitions.
Maintenance
No periodic maintenance or calibration is required for the
digital input modules. There are no user replaceable parts
inside these modules. In safety critical input applications, the
inputs should be dynamically transitioned at a period not
greater than six months.
Safety Considerations
The DC voltage digital input modules are TÜV certified as