Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 49)

Programming
Chapter 3
3Ć6
The PID module prompts the sequencing of block transfers. The write
block transfer instruction in the user program contains the data table
address of the first word of the block file to be transferred. By
manipulating this address, different data block files can be transferred
with the same write block transfer instruction.
There are three control bits which are associated with the handshaking of
the load/enter sequence.
The load bit is set in the dynamic block to allow the PID module to
accept dynamic block data and to load loop 1 and loop 2 constants into
the module’s buffer.
The ready bit is returned in the status block to indicate that the write
block transfers were acceptable and that the module is able to process
the information.
The enter bit is set to activate the information in the module’s buffer
and to start control based on the new parameters transferred during the
load/enter sequence.
An overview of the load/enter sequence is presented in Figure 3.4.
Additional information can be found in sections titled Power-up
Load/Enter Sequence and Load/Enter Sequence.