Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 106)

Programming
Chapter 3
3Ć63
PowerĆUp Load/Enter Sequence
A power-up load/enter sequence is required for initial power-up or after
the module resets itself from the restoration of +5VDC power. This
sequence is a series of block transfers that begins with the module
clearing its memory of all previously stored data.
There are two control bits and four status bits used in the power-up
load/enter sequence (Table 3.L).
The power-up load/enter sequence is outlined below and illustrated in
Figure 3.21. Refer to Block Transfer Sequencing, section titled Block
Transfer Sequencing.
Transfer 1 - The processor reads the status block in the first block
transfer. Word W58 will be returned with the power-up bit W58 B13 set
to 1 indicating that the PID module has just been powered-up and has not
yet been initialized.
The RUN LED on the module will be flashing. Other LEDs will be off.
This indicates the module has power but has not yet been programmed.
Transfer 2 - The processor writes the dynamic block data to the module
in this block transfer. Load bit W01 B06 is set to 1.
Transfer 3 - The read block transfer will prompt the loading of loop 1
constants by returning the loop 1 block start address W04 in word W59.
The status block will contain the power-up bit W58 B13 reset 0.
Transfer 4 - The write block transfer must contain the loop 1 constants.
If incorrect values are transferred during initialization, the load sequence
is held at this point until values are corrected. The load/enter sequence
then resumes.
Transfer 5 - The read block transfer will prompt the loading of loop 2
constants by returning the loop 2 block start address W11 in the word
W59.
Transfer 6 - The write block transfer must contain the loop 2 constants.
Transfer 7 - The read block transfer will prompt the dynamic block by
returning the dynamic block start address W03 in word W59. This
transfer will contain the ready bit W58 B12 set to 1.