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GFK-0825F Chapter 4 Operation 4-19
4
Backing Up BIU Outputs with a Micro Field Processor
The Micro Field Processor can take over control of outputs normally provided from the network by
the Bus Interface Unit, if those outputs become unavailable. This technique requires the addition of
ladder logic to the application program.
To create this backup capability for one or more modules, do the following:
1. Configure the module outputs to the Bus Interface Unit
outside
of the BIU's network map (that
is, the data exchanged with the bus), but
within
the I/O range of the MFP.
For example:
Module Outputs
Q00025-Q00040
Q00001-Q00024
Q00025-Q00040
Network
Map
(BIU) References Assigned
to Micro Field Processor
Q00025-Q00040
Q00001-Q00024
Q00041-Q00128
(BIU) References Assigned
to Module Outputs
2. Create variables to monitor the presence of network outputs, BIU outputs, and to serve as a
heartbeat to verify the presence of the network.
For the example, the variables are:
VARIABLE DECLARATION TABLE
REFERENCE NICKNAME
REFERENCE DESCRIPTION
I00001 NETOUTS Network outputs
I00017 NETPRES Network presence status
Q00001 STOUTS Station outputs
3. Add ladder logic like the following example to the application program.