Rockwell Automation 1791-XXXX ANALOG BLOCK I/O - Manual (Page 51)

Chapter
6
6-1
Programming Your Analog Block I/O Module
In this chapter, we describe
block transfer programming
sample programs in the PLC-3 and PLC-5 processors
module scan time issues
Your module communicates with the processor through bidirectional block
transfers. This is the sequential operation of both read and write block
transfer instructions.
For the analog block I/O modules, block transfer writes (BTWs) can
perform two different functions.
If you want to: Description This type of BTW is called:
configure the module
This involves setting the bits which enable the
programmable features of the module, such as
scaling, alarming, real time sampling, etc.
the configuration BTW"
send data to the output channels
of those modules having outputs
This type of BTW is generally shorter in length
than the configuring BTW because it does not
configure the module each time it is initiated.
the output update BTW"
The following example 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 analog module works with a default configuration upon powerup as
long as a block transfer write (BTW) has not been initiated. The default
mode is binary scaling and the input range is +/–10V. In the default mode,
the alarms are off and the outputs are reset at 0.
Your program should monitor status bits (such as power up status, bad
configuration, output out of range, alarms, etc.) and block transfer read
activity.
The following example programs illustrate the minimum programming
required for communication to take place.
Chapter Objectives
Block Transfer
Programming