Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 47)

Programming
Chapter 3
3Ć4
The status block SB is a read block transfer file used to report the current
status of the PID module and any alarm condition detected by the module.
The transfer of the status block is also used to prompt the next write block
transfer.
Figure 3.2 illustrates the multiple block concept.
Figure 3.2
Multiple Block Concept
Dynamic
Block
Loop 1
Constants
Block
Loop 2
Constants
Block
Status
Block
PID Module
Write Block
Transfer
Write Block
Transfer
Write Block
Transfer
Read Block
Transfer
PC Processor
Data Table
11094
PC Processor Memory Requirements
The PID module requires multiple files in the C processor data table to
store the different blocks of data. Storage requirements are determined by
the features selected. The module can be configured for one or two loops
with either standard or expanded features. There are four different
memory requirements for storing block of data (Figure 3.3).
User program memory requirements will vary depending on the
application. Examples are shown in appendicies B and C.