GE GFK-0825F Operation of the BIU with a Micro Field Processor

4-14 Field Control™ Genius® Bus Interface Unit User’s Manual – October 1999 GFK-0825F

Operation of the BIU with a Micro Field Processor

The Micro Field Processor (MFP) is a specialized Micro PLC that provides local input/output logic

within a Field Control I/O station. The MFP itself does not perform an I/O scan; that function is

performed by the BIU.

Automatic operation of the Micro Field Processor must be synchronized with that of the BIU.

Synchronization between the MFP and the BIU occurs at the following point s:

1. The MFP waits for group data from the BIU.

2. The MFP waits for its input reference parameter data (see page for a discussion of reference

parameter data) from th e BIU. After receiving the refer ence parameter data fr om th e BIU, the

MFP solves its logic program.

3. After solving its logic program, the MFP waits for the BIU to request its output reference

parameter data. Or, if the MFP is still busy, the BIU waits for the Micro Field Processor to

finish solving its logic.

4. The MFP waits for the BIU to request any group data from the MFP.

The diagram on the next page shows the basic points of synchronization between a BIU and an

MFP. The Micro Field Processor always performs housekeeping and programmer window

functions regardless of the combination of BIU and MFP modes.

The MFP itself has the following configurable references:

I001 to I512

Q001 to Q512

AI001 to AI128

AQ001 to AQ128

References used by the host may map to th ese MFP references, although that i s n ot n ecessa r y.

Appendix D gives examples of I/O reference assignments.

In the Standard Program Sweep mode, the Micro Field Processor executes each sweep as quickly

as possible with a varyin g amount of time consumed each sweep.

In the Constant Sweep Time mode, each sweep consumes the same amount of time. This time is

configurable to be from 5 to 200 milliseconds.

When the MFP is in Stop mode, the application program is not executed. In this mode, it is

possible to choose whether or not the I/O is scanned (internally, by the MFP) and wheth er

communications with th e programmer will contin ue.

If the BIU requests da ta from the Micro Field Pr ocessor while the MFP is in St op Fault mode, the

requested data will either be defaulted or held in its last state, depending on the configurati on of the MFP.

In Stop-No I/O mode, the MFP updates its int erna l I/AI tables with data received from the BIU,

and sends zeros for all data (reference or group) to the BIU.