Honeywell UMC800 Reference Manual page 149

2.50 PID Function Block,
Inputs, continued
SWI = Switch Inputs (from SWO on LPSW function block)
0 = No Change
1 = Initiate Autotuning
2 = Change Control Action
4 = Force Bumpless Transfer
8 = Switch to Tune Set 1
16 = Switch to Tune Set 2
MDRQI = External Mode request (typically connected to the MDRQO output of a MDSW function block
that encoded discrete switch inputs).
0 = No Change
1 = Manual Mode Request
2 = Auto Mode Request
4 = Local Mode Request
8 = Remote Mode Request
BCI = Back Calculation Input (for blocks used as Cascade Primary)—See Note 2.
Outputs
OUT = Control Output
WSP = Working Setpoint in Engineering Units for monitoring
AL1 = Alarm 1 - Digital Signal
AL2 = Alarm 2 - Digital Signal
ATI = Autotune Indicator (ON = Autotune in Progress)
MODE = Loop mode status (typically connected to the Mode Flags block for encoding). Value indicates
modes as follows:
0.0 RSP AUTO
1.0 RSP MAN
2.0 RSP Initialization Manual (See Note 1)
3.0 RSP Local Override (See Note 1)
4.0 LSP AUTO
5.0 LSP MAN
6.0 LSP Initialization Manual (See Note 1)
7.0 LSP Local Override (See Note 1)
BCO - Back Calculation Output (for blocks used as Cascade Secondary)—See Note 2.
NOTE 1.
When a request to change from Auto to manual is received and:
- the request comes from the operator Interface, the request is ignored.
- the request comes from the Mode Switch (MDSW) function block, the request is retained and when leaving the
Initialization Mode or Local Override Mode the loop will go to manual.
NOTE 2.
BCO output is provided for applications where the block is used as a cascade secondary.
BCI input is provided for applications where the block is used as a cascade primary. When the BCO output of a
secondary loop is connected to the BCI input of a primary loop, bumpless transfer is achieved when the secondary is
switched into remote setpoint (i.e., cascade) mode. In addition, the primary loop is prevented from reset windup when
the secondary is de-coupled from the process. The secondary is de-coupled from the process when it is in local setpoint
mode or manual output mode or has reached a setpoint or output limit or is integral limiting because of it's BCI input.
For example, see Figure
3/99
continued
2-49.
Function Block Reference Guide
Function Blocks
Continued next page
139