Spectrum Controls 1771sc-IFE32 - Manual (Page 23)

Chapter 3: Module Programming 13
Chapter 3
Module Programming
Chapter Objectives: Chapter Objectives: Chapter Objectives: Chapter Objectives: Chapter Objectives:
In this chapter we describe:
·
block transfer programming
· sample programs for PLC-5 processors
· module scan time issues
Bloc Bloc Bloc Bloc Block k k k k T T T T Transf ransf ransf ransf ransfer Pr er Pr er Pr er Pr er Programming ogramming ogramming ogramming ogramming
Your module communicates with your processor through bi-directional block trans-
fers. This is the sequential operation of both read and write block transfer instruc-
tions.
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’s green LED will flash unit the module is programmed.
The module will work with a default configuration of zeroes entered in all five words
of a five word BTW configuration block. Upon writing zeros to the configuration
word the LED will stop blinking. See the configuration default section to understand
what this configuration will look like. Also, refer to Appendix C for example configura-
tion blocks and instruction addresses to get started.