Rockwell-automation 1771-DMC_DMC1_DMC4_DXPS Control Coprocessor User M Instrukcja Użytkownika Pobierz pdf (Strona 66)

Chapter 5

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5-6

The control coprocessor communicates with a standalone-mode

programmable controller using backplane-interface (BPI) functions. The

communication is via the 1771 I/O chassis backplane. You can also use

the BPI functions when you have a PLC-5 programmable controller

directly connected to the control coprocessor.

For backplane communication, the control coprocessor appears to the

programmable controller as a 16-bit, bidirectional I/O module. The control

coprocessor can perform both discrete- and block-data transfers.

Important: The only bits available for use by the application program

are the upper 8 bits (10-17). The lower 8 bits (0-7) are reserved for

block transfer, even if there are no block transfers programmed to the

control coprocessor.

You must prepare a control-logic program in the programmable controller

to initiate block transfer and/or discrete reads and writes with the control

coprocessor. See page 5-21 for an example of a control-logic program.

ATTENTION: The control coprocessor will not communicate

via discrete or block transfer in any chassis (remote or local) set

for 2-slot addressing; however, 1-slot and 1/2-slot addressing

are valid configurations for a chassis that contains a control

coprocessor communicating via discrete or block transfer with a

PLC processor.

Update Discrete Data

Use BPI_DISCRETE to get the updated output-image word from the

PLC-5 programmable controller or send the input-image word to the

controller. The function determines whether it is an input or an

output word.

Accomplish BlockĆTransfer Reads and Writes

Use BPI_WRITE and BPI_READ routines to allow PLC-5 programmable-

controller reads and writes of block data across the backplane interface.

Function What It Does

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     ! "     

      ! "     

How to Use BPI Functions

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Rockwell-automation 1771-DMC_DMC1_DMC4_DXPS Control Coprocessor User M Instrukcja Użytkownika Strona 66