GE GFK-0825F How the Network Backs Up MFP Outputs

4-18 Field Control™ Genius® Bus Interface Unit User’s Manual – October 1999 GFK-0825F
4
How the Network Backs Up MFP Outputs
This technique works because of the synchronization between the operations of the Bus Interface
Unit and the Micro Field Processor. The diagram below shows details of the BIU/MFP
synchronization process. The numbers on the left side are the same as the numbers on the
synchronization diagram.
Move all outputs within BIU netw ork
map from the Geni us communicatio ns
buffers to th e BIU internal ta bles
Read all reference input parameters from
a Synchronization module
7
8
MFP provides data
to BIU
BIU Waits if
MFP is busy
Micro Field ProcessorBus Interface Unit
10 Send all outputs to convention al m odules
The Bus Interface Unit recei ves output data for the back ed-up output module(s) from the Genius
bus (step 7). In step 8, the BIU r eceives data from the Micro Field Processor. Any data with the
same reference assign m ents overwrites the data alr eady received from the bus. Wh en th e BI U sen ds
outputs to I/O modules (st ep 10), it sends the most recent contents of the output referen ces. If the
MFP has not provided fresh output data (for example, if the MFP has stopped communicating with
the BIU), the outputs from the network are sent to the modules instead. Note that this will not work
if MFP outputs are configured to default instead of Hold Last State, because selecti ng default
causes the BIU to write default values into the output references at step 8.