Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 60)

Programming
Chapter 3
3Ć17
Loop Constants Block: W18ĆW36 for Loop 1, W38ĆW56 for Loop 2
Loop block are write block transfer files of up to 19 words. They contain
loop constants and are used to establish the loop features of the PID
module. Loop 1 block must be used when the PID module is controlling
only one loop. The loop 1 and loop 2 blocks are used for 2-loop control.
Three control words are used to select the features in each loop. They are
loop control words A and B, and the expanded loop control word. The
remaining words are used to store values which typically remain constant
during normal operation.
Loop 1 words W18 through W29 are programmed if standard features are
selected by W01 B14 = 0. The entire block (words W18 through W36) is
programmed if the expanded loop features are selected by W01 B14 = 1.
When both loops are used, loop 2 words W 38 through W49 must also be
programmed for standard features when W01 B14 = 0. The entire loop 2
block (words W38 through W56) must also be programmed if the loop 2
expanded features are selected by W01 B14 = 1.
To change the programming of any word or bit in the loop blocks, a
load/enter sequence must be initiated.
The 19 words that comprise the loop block are defined in the paragraphs
that follow. Table 3.C lists the loop block words. All the words of the
dynamic block, loop blocks and status block are listed in Table 3.J,
Figure 3.13 and Figure 3.14 found at the end of section titled Word and
Bit Description.
NOTE: Because the loop 1 and loop 2 blocks are very similar, the
definitions of the words and bits will be presented once for loop 1.
Reference to loop 2 will be indicated by parentheses, i.e. (loop 2).