Rockwell Automation 1794-XXXX FLEX I/O High-Density Analog Modules - Manual (Page 75)

67 Publication 1794-UM062A-EN-P - September 2012
Appendix D
Module Programming
Overview This Appendix serves as a reference to users of the PLC Processors to program
their modules.
To initiate communication between the analog input and output modules and
your PLC processor, you must enter block transfer instructions into your ladder
logic program. Use this chapter to enter the necessary block transfer instructions
into your ladder logic program.
Block Transfer
Programming Your module communicates with the processor through bidirectional block
transfers. This is the sequential operation of both read and write block transfer
instructions.
A configuration block transfer write (BTW) is initiated when the analog module
is first powered up, and subsequently only when the programmer wants to enable
or disable features of the module. The configuration BTW sets the bits which
enable the programmable features of the module, such as scaling, alarms, ranges,
etc. Block transfer reads are performed to retrieve information from the module.
Block transfer read (BTR) programming moves status and data from the module
to the processor’s data table. The processor user program initiates the request to
transfer data from the module to the processor. The transferred words contain
module status, channel status and input data from the module.
The following sample programs are minimum programs; all rungs and
conditioning must be included in your application program. You can disable
BTRs, or add interlocks to prevent writes if desired. Do not eliminate any storage
bits or interlocks included in the sample programs. If interlocks are removed, the
program may not work properly.
Your program should monitor status bits, block transfer read and block transfer
write activity.
Sample Programs for FLEX
I/O Analog Modules The following sample programs show you how to use your analog module
efficiently when operating with a programmable controller.
These programs show you how to:
ATTENTION: If the analog module is not powered up before the
remote I/O adapter, the adapter will not recognize the module.
Make certain that the analog module is installed and powered
before or simultaneously with the remote I/O adapter. If the
adapter does not establish communication with the module, cycle
power to the adapter.