EAF
Process Control Instructions
Chapter 16
16-7
Important:Do not set this bit when entering the PID instruction in
Program mode. Since the PID instruction has not been executed yet, there
is nothing to resume in Run mode. Set this bit only after the PID
instruction has been executed in Run mode at least once.
Bumpless Transfer with Proportional Controllers
The Bumpless Transfer bit is located in the PID Control Block Word 02,
Bit 11. This bit provides a bumpless transfer from manual mode to auto
mode for loops that have no integral term (K
I
=0).
When this bit is set, a Bias value is calculated and stored in the PID control
file to account for the difference between the Proportional Term and the
manually adjusted Control Output (CO). When you switch back to auto
mode, this Bias value is added to the PID calculation to produce a CO
value equal to the last manually adjusted CO value (thus achieving a
bumpless transfer).
Important:In this mode, the range on the Feedforward is 0-FFFF
(hexadecimal). The Feedforward/Bias Sign Bit (Word 02 Bit 02) is
still valid.
Table 16.B, Table 16.C, Table 16.D and Table 16.E explain the functions of
all of the words and bits in the PID Control Block.
