Unexpected Loss of Device faults
Loss of Device faults for currently connected devices may appear in the PLC I/O Fault
table and/or PNC001 local log when the PNC001 is reset via its reset pushbutton.
Unintended operation of
PNIO_DEV_COMM function block
The power flow output of the PNIO_DEV_COMM function block provides validation of
the input parameters and confirms that the PNC001 has locally processed the
configuration of the specified I/O Device. As currently implemented, the power flow
output will not turn ON until after the PNC001 has made its first attempt to connect to
the specified I/O Device. Therefore, we recommend the user not rely on power flow
output for parameter validation.
IOC SW Fault with large
configurations
When storing a configuration to the PNC001 that is close to the upper limit of the
controlling PLC’s user memory, the store may fail with an IOC SW Fault logged in the
PLC’s I/O Fault table. The work-around to resolve this issue is to clear the PLC’s existing
configuration and store the configuration again.
The Push and Hold behavior of the
PNC001 Restart Pushbutton
results in the CRU320 taking up to
1 second to detect that PNC001 is
no longer available
When the PNC001 reset button is held down for more than 1 second, the CRU320 can
take up to 1 second to detect the loss of the PNC001 (after the PNC001 module resets).
This causes a delay in the CPU signaling the Loss of IOC, and in taking the appropriate
fault actions (setting point faults, stopping the controller if Loss of or Missing I/O
Controller faults are configured as Fatal, etc.)
In a Hot Standby Redundancy System, if the system is synchronized and the PNC001 in
question is in the active unit, this also causes a delay in the redundant system failing
over to the backup unit. If this delay exceeds the Redundancy Data Hold Time (RDHT)
for a given I/O Device, that IO Device will disconnect from the backup unit before the
failover occurs.
It is not recommended to use the PNC001 reset button in a normally operating system.
If the reset button must be used, it is recommended to first attempt a brief press and
release of the PNC001 reset button (the PNC001 should reset as soon as the button is
released). Only if the first attempt fails should the PNC001 button be depressed until the
PNC001 resets (approximately 2-3 seconds).
Breaking and reconnecting an
MRP ring by pulling either of the
two MRM ports of the PNC001
causes extra ring open/close faults
In some cases, if the network is broken and repaired at either of the two ring ports of a
PNC001 configured to be the MRM, extra I/O Bus Fault-Redundant Ethernet network
ring broken (open) and I/O Bus Fault-Redundant Ethernet network ring okay (closed)
faults are logged in both the I/O Fault Table and the PNC001 Local Log when the ring is
repaired.
These additional faults can safely be ignored as long as the last fault to be logged is I/O
Bus Fault-Redundant Ethernet network ring okay (closed).
Additional verification of ring status can be obtained by issuing a show rdnMedia
command using the PNC001’s CLI interface.
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