Siemens SIMATIC S5 Manual page 215

Function
The following commands are only valid in conjunction with a message number:
KS = AS
KS = AE
KS = AB
KS = HB
KS = IW
5–10
Change setpoints
Parameter T-NR: KF +0 to +15
If a change is made in data words DWn to DWn + 6 in messages
0 to 15, it is sufficient to transfer the message (T-NR) to the
module with the command AS.
Change the parameters of a controller
Parameter T-NR: KF +0 to +15
If the parameters of a controller are changed, the appropriate
message must be transferred with the command AE. The
parameters of the selected controller are recalculated on the
module. (Two messages per controller are transferred.)
Switch over to automatic operation
Parameter T-NR: KF +0 to +12
With the AB command (automatic operation) the function block
resets bit 0 of control byte 2 in the specified controller message
(parameter T-NR) and transfers control byte 2 to the module.
Switch over to manual operation
Parameter T-NR: KF +0 to +12
With the HB command (manual operation) the function block sets
bit 0 of control byte 2 in the specified controller message
(parameter T-NR) and transfers control byte 2 to the module.
Read actual value, read current values
Parameter T-NR: KF + 17 to + 21 (e.g. actual values,
manipulated variables, minimum values etc.)
The actual values are only read when this is requested with the
command IW. The message number in which the required actual
values are located must be specified. The structure in the actual
value messages is described in the Instructions
(C79000-B8576-C859).
IP244
C79000–B8576–C861–02