6 - 8 WBPEEUI240751C0
Function Codes
The Harmony controller allows using both I/O block and rack
I/O function codes concurrently to communicate with both
Harmony I/O blocks and Harmony rack I/O devices simulta-
neously.
I/O Device Definition (FC 221)
The I/O device definition function code (FC 221) is mainly
used to group the various I/O channel function codes of an
I/O block. The function code supports up to 24 input or out-
put channels (i.e., I/O channel function codes). Besides group-
ing the I/O channels, the function code is also responsible for:
• I/O block and channel summary status reporting.
• Duplicate device label checking.
• Configuration verification.
• Redundancy checking and failover.
• Generating problem reports.
• Override, simulation, and status error inhibit permit.
Refer to Section 8 for I/O block status reporting details.
Function code specifications:
• Contain an I/O block device label. This associates the
function code with a specific I/O block.
• Link I/O channel function codes. These function codes
interface the I/O block inputs and outputs.
• Permit override, simulation, and status error inhibit modes
for all linked I/O channels (i.e., master switch).
• Control I/O block status reporting. A status error inhibit
condition prevents I/O channel errors from being included
in the I/O block device status report made to the control-
ler.
• Enable redundant I/O module checking.
• Identify an external cold junction reference for thermocou-
ple inputs.
These are just some of the function code capabilities. Refer to
the Function Code Application Manual for detailed function
code descriptions, specifications, outputs, and capabilities.
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