Rockwell Automation 1771-IFF/A,D17716.5.116 FAST ANALOG INPUT MODULE - Manual (Page 45)

Chapter
5
Publication 1771Ć6.5.116 - July 1996
Module Programming
In this chapter we describe:
•
block transfer programming
•
sample programs in the PLC-2, PLC-3 and PLC-5 processors
•
module scan time issues
Your module communicates with your processor through
bidirectional block transfers. This is the sequential operation of both
read and write block transfer instructions.
The block transfer write (BTW) instruction is initiated when the
analog module is first powered up, and subsequently only when the
programmer wants to write a new configuration to the module. At all
other times the module is basically in a repetitive block transfer read
(BTR) mode.
The application programs for the three processor families were
written to accomplish this handshaking in the described manner.
They are minimum programs; all the rungs and conditioning must be
included in your application program. If you wish to disable BTRs
for any reason, or add interlocks to the BTW rung to prevent writes
from happening at certain times, you are allowed to do it. You may
not eliminate any storage bits or interlocks that are included in our
examples. If interlocks are removed, the program may not work
properly.
The analog input module will work with a default configuration
of zeroes entered in all five words of a five word BTW
configuration block. See the configuration default section to
understand what this configuration will look like. Also, refer to
Appendix B for example configuration blocks and instruction
addresses to get started.
!
ATTENTION: In PLC-2 family processors you must
not enable both the read and write instructions at the
same time. Undesirable data could transfer, resulting in
unpredictable machine operation. Using the prescribed
programs will prevent this situation.
Chapter Objectives
Block Transfer
Programming