Siemens SIMATIC S5-90U System Manual page 254

Integrated Blocks and Their Functions
Table 9-3. Description of the Control Bits in Control Word "STEU"
Control Name
Bit
0 AUTO
1 XZ EIN
2 REG AUS
3 GESCHW
4 HANDART
5 NO Z
6 and 7 -
8 to 15 -
The control program can be supplied with fixed values or parameters. Parameters are input via the
assigned data words. The controller is based on a PID algorithm. Its output signal can be either a
manipulated variable (positioning algorithm) or a manipulated variable modification (correction rate
algorithm).
9-10
Signal
State
0 Manual mode
The following variables are updated in Manual mode:
1) X , XW and PW
K K-1
2) XZ , XZ and PZ
K K-1
3) Z and Z , when STEU bit 5=0
K K-1
Variable dD is set to 0: The algorithm is not computed.
K-1
1 Automatic mode
0 XW is forwarded to the differentiator. The XZ input is ignored.
k
A variable other than XW
1
XZ input.
0 Normal controller processing
When the controller is invoked (OB251), all variables (DW 18 to
1
DW 48 ) with the exception of K, R, TI, TD, BGOG, BGUG, YH
W are reset in the controller DB. The controller is deactivated.
k
0 Positioning algorithm
1 Correction rate algorithm
0 When GESCHW=0:
Following the transfer to Manual mode, the specified manipulated
variable value YA is adjusted exponentially to the manual value in
four sampling steps. Additional manual values are then forwarded
immediately to the controller output.
When GESCHW=1:
The manual values are forwarded immediately to the controller
output. The limiting values are in force in Manual mode.
1 When GESCHW=0:
The manipulated variable last output is retained.
When GESCHW=1:
Correction increment dY
0 With feedforward control
1 No feedforward control
These bits are not assigned.
The PID algorithm uses these bits as auxiliary flags.
Description
K-1
, when STEU bit 1=1
K-1
is forwarded to the differentiator via the
k
is set to zero.
K
EWA 4NEB 812 6115-02b
S5-90U/S5-95U
and
k