Rockwell Automation 1771-VHSC , D17716.5.74 Very High S - Manual (Page 35)

Chapter
3
Module Programming
In this chapter we describe:
block transfer programming
sample programs in the PLC-2, PLC-3 and PLC-5 processors
Your module communicates with the processor through bidirectional
block transfers. This is the sequential operation of both read and
write block transfer instructions.
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.
Optionally, the block transfer write (BTW) instruction is initiated
when the 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.
Your 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.
The following example programs illustrate the minimum
programming required for communication to take place.
Chapter Objectives
Block Transfer
Programming