Rockwell Automation 1771-QRD PULS FLOWMTR - Manual (Page 37)

More on Overrange and Overflow
Chapter 5
5–5
The example in Figure 5.2 detects a count overflow on Channel 1, and
resets the overflow bit for that channel with a Block Transfer Write
command. The ladder logic also keeps track of the total number of counts
received at the channel 1 inputs.
A similar ladder could reset the overflow bits for channels 2, 3, and 4 by
setting bits 165, 166, and 167 of data table B3. The actual totals for the
four channels could be reset by setting bits 160, 161, 162, and 163 of data
table B3.
Although not shown in the previous examples, it is good PLC–5
programming procedure to include a rung to reset the EN bit of a block
transfer control file when the ER bit is set, when continuous transfers are
used.
In this chapter, you learned the structure of the acknowledge code sent
from the QRD and how to reset the totalizer(s) and/or the overflow flags.
You also learned about the overrange condition, and how to detect it.
Finally, you learned the structure of the Block Transfer Write command
that is sent to the QRD Module for resetting overflow flags and/or
totalizer(s).
Chapter Summary