Siemens SIMATIC S7 System Manual page 321

Loop table
The loop table is 80 bytes long and has the format shown in the following table.
Offset Field
0 Process variable (PV
4 Setpoint (SP
n
8 Output (M )
n
12 Gain (K )
C
16 Sample time (T
20 Integral time or reset (T
24 Derivative time or rate (T
28 Bias (MX)
32 Previous process variable
(PV )
n-1
36 to 79 Reserved for auto-tuning variables. Refer to PID loop definition table (Page 582) for details.
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
Format
) REAL
n
) REAL
REAL
REAL
) REAL
S
) REAL
I
) REAL
D
REAL
REAL
Type Description
In Contains the process variable, which must be scaled
between 0.0 and 1.0.
In Contains the setpoint, which must be scaled be-
tween 0.0 and 1.0.
In/Out Contains the calculated output, scaled between 0.0
and 1.0.
In Contains the gain, which is a proportional constant.
Can be a positive or negative number.
In Contains the sample time, in seconds. Must be a
positive number.
In Contains the integral time or reset, in minutes. Must
be a positive number.
In Contains the derivative time or rate, in minutes. Must
be a positive number.
In/Out Contains the bias or integral sum value between 0.0
and 1.0.
In/Out Contains the value of the process variable stored
from the last execution of the PID instruction.
Program instructions
7.9 PID
321