Rockwell Automation 1771-IS 5V DC INPUT MOD - Manual (Page 43)

Programming and Operation
Chapter 3
3-24
This can be done by examining the block transfer done bit for an ON
condition. An EXAMINE ON instruction addressed to the done bit
should be a logic condition for any further manipulation of transferred
data. The done bit for the PLC-2 family and PLC-3 programming
example is 112/17 and WB001:0010/15, respectively.
WARNING: Program the examination of the block transfer
done bit as a condition for subsequent data manipulation
following each block transfer. Otherwise, invalid data could be
operated upon causing unexpected machine operation with
possible damage to equipment and/or injury to personnel.
The communication fault bit, bit 12 of the diagnostic word, can be
examined as an additional buffering condition. This can be done by using
an EXAMINE OFF instruction addressed to bit 12 of the diagnostic
word’s location in the data table (060/12 for PLC-2 family,
WD002:0012/12 for PLC-3 in this example). If transfer was aborted, the
next transfer of data would contain bit 12 ON, in the diagnostic word.