Rockwell Automation 1771-OFE/B Analog Output Module User Manual - Manual (Page 37)

Chapter
4
Publication 1771Ć6.5.30 - November 1998
Module Programming
In this chapter you will read about:
For information on See page
Block Transfer with the Analog Output Module . . . . . . . . . . . . 4-1
Block tTansfer Programming Formats . . . . . . . . . . . . . . . . . . 4-1
Block tTansfer Programming Formats - PLC-2 Family
Processors only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Block tTansfer Programming Formats - PLC-3 Family
Processors only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
Block tTansfer Programming Formats - PLC-5 Family
Processors only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
Other Programming Considerations . . . . . . . . . . . . . . . . . . . 4-10
System Expansion Recommendations Ć PLCĆ2 Processors
Only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13
If you have used other intelligent I/O modules, you may be familiar
with bidirectional block transfer programming. Bidirectional block
transfer is the sequential performance of both read and write
operations. Typically, in previous bidirectional block transfer
modules, the enable bits of both read and write instructions could be
set ON at the same time.
Although the module can perform both read and write operations, the
module does not allow the enable bit of both read and write
instructions to be set ON at the same time. Your program must
toggle requests for the read and write instructions as shown in our
sample programs.
!
ATTENTION: At no time should both the read and
write instructions be enabled. Undesirable data could
transfer resulting in unpredictable machine operation.
In order for the processor to exchange data with the output module,
you must include block transfer read and write instructions in your
program. The types of programming formats available for block
transfer are block format and multiple GET instructions. You can
program most processors that use the 1771 I/O structure with block
format instructions. Exceptions are the Mini-PLC-2 (cat. no.
1772-LN3) and PLC-2/20 (cat. no. 1772-LP1, -LP2) processors;
they use the multiple GET instructions. Refer to Appendix B for
information on block transfer with the Mini-PLC-2 and the
PLC-2/20.
There are three types of block format instructions--one each for the
PLC-2, PLC-3, and PLC-5 processors. Each is described in the
paragraphs that follow.
What This Chapter
Contains
Block Transfer with the
Analog Output Module
Block Transfer
Programming Formats