Siemens SIMATIC S7-200 System Manual page 166

S7-200 Programmable Controller System Manual
Loop Table
The loop table is 80 bytes long and has the format shown in Table 6-44.
Table 6-44 Loop Table
Offset Field
0 Process variable
(PV )
n
4 Setpoint
(SP )
n
8 Output
(M )
n
12 Gain
(K )
C
16 Sample time
(T )
S
20 Integral time or reset
(T )
I
24 Derivative time or rate
(T )
D
28 Bias
(MX)
32 Previous process
variable (PV
36 to Reserved for auto-tuning variables. Refer to Table 15-1 for details.
79
152
Format
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
REAL
)
n- -1
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
between 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.