Table of Contents
Advertisement
Programming Considerations
Summary
When you specify the default block length (00), the following
considerations apply for PLC-2 family processors:
You can and should enable the read and write instructions in the same
scan (separate but equal input conditions).
The module decides which operation is performed first when both
instructions are enabled in the same scan.
Alternate operation is performed in a subsequent scan.
Do not operate on transferred data until the done bit is set.
When you examine the read and write files, 64 words appear to be moved;
however, the processor writes only 20 words and reads only two words in
any block-transfer operation.
WARNING: When the block lengths of bidirectional
block-transfer instructions are set to unequal values, do not
enable the rung containing the alternate instruction until the
done bit of the first transfer is set. If you enable them in the
same scan, the number of words transferred may not be the
number intended, invalid data could be operated upon in
subsequent scans, or output devices could be controlled by
invalid data. Unexpected and/or hazardous machine operation
could occur. Damage to equipment and/or personal injury could
result.
This chapter gave a description of the file parameters for programming
block-transfer-read and -write operations for the absolute encoder module.
It also gave several programming examples and considerations for use
with the absolute encoder module. The next chapter describes
troubleshooting the module.
Chapter 4
Module/Processor Communication
4 7
Advertisement
Table of Contents
