How To Change Loop Modes - Automation Direct DL05 User Manual

Using Other PID Features
It's a good idea to understand the special features of the DL05 and how to use them. You may
want to incorporate some of these features for your PID.

How to Change Loop Modes

The first three bits of the PID Mode 1 word (V+00) request
the operating mode of the corresponding loop. Note: These
bits are mode change requests, not commands (certain
conditions can prohibit a particular mode change – see next
page).
The normal state of these mode request bits is "000". To request a mode change, you must
SET the corresponding bit to a "1", using a one-shot. The PID loop controller automatically
resets the bits back to "000" after it reads the mode change request. Methods of requesting
mode changes are:
• DirectSOFT 5's PID View – this is the easiest method. Use the drop-down menu, or click on one
of the radio buttons, and the appropriate bit will get set.
• Ladder program– ladder logic can request any loop mode when the PLC is in Run Mode. This will
be necessary after application startup if mode changes are part of the application.
Use the rung shown to the right to SET the mode bit (do not use
an OUT coil). On a 0–1 transition of X0, the rung sets the Auto bit
equal to 1. The loop controller resets it.
• Operator panel – interface the operator's panel to ladder logic
using standard methods, then use the logic to the right to set the mode bit.
Since mode changes can only be requested, the PID loop controller will decide when to permit
mode changes and provide the loop mode status. It reports the current mode on bits 0, 1, and
2 of the Loop Mode/Alarm Status word, location V+06 in the loop table. The parallel
request/monitoring functions are shown in the figure below. The figure also shows the two
possible mode-dependent SP sources, and the two possible Control Output sources.
Control Output
from another loop
Normal Source
Mode Request
Cascade
Setpoint
Auto/Manual
PID Mode 1 Setting V+00
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Cascade
Automatic
DL05 Micro PLC User Manual, 6th Edition, Rev. A
Chapter 8: PID Loop Operation
Bit
Input from Operator
Loop
Error Term
Calculation
+
–
Process Variable
Mode Select
PID Mode
Control
Loop Mode and Alarm Status V+06
0 Bit 15 14
Mode Monitoring
Manual
PID Mode 1 Setting V+00
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Cascade
Automatic
Go to Auto Mode
X0
B2000.1
Manual
Control Output
Auto/Cascade
13 12 11 10 9 8 7 6 5 4 3 2 1 0
Cascade Manual
Automatic
1
2
3
0
4
Manual
5
6
7
8
9
SET
10
11
12
13
14
A
B
C
D
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