Rockwell Automation 1771-IXE/D Thermocouple/Millivolt Input Module User Manual - Manual (Page 23)

Chapter
3
Publication 1771Ć6.5.130 Ć May 1999
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 the 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 following example programs accomplish this handshaking
routine. These 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 input module will work with a default configuration of
all zeroes entered in the configuration block. See the configuration
default section to understand what this configuration looks like.
Also, refer to Appendix B for example configuration blocks and
instruction addresses to get started.
Your program should monitor status bits (such as overrange,
underrange, 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