Siemens SIMATIC S5 Manual page 256

Application of the Function Block
Byte for direct functions
With direct access by the user program to the IP 244 temperature controller module, a byte (right
data byte DR2) in data block DB-A, stipulates that the execution of certain commands has priority.
The commands of this byte are known as direct functions. They are executed with priority over the
commands in DW 1 or commands started by the parameters BEF and ANST. By setting a bit in this
byte, you can transfer a command word as a direct function.
If one of the commands S1, S2, T1, T2, G1 or G2 is set and a direct function is triggered in the same
FB 162 call, both commands are transferred to the module in one message.
In this case, data word DW 1 (DB-A) is also set to KH0000, or the parameter ANST is reset.
Select direct functions:
D 2.0: start bit, read curve values channel 13
You set this bit to trigger the reading of 60 curve values on the module. FB 162
resets the bit immediately after the command has been transferred to the module.
You can set the bit again at any time, even if the last job is not yet complete. Only
the last job triggered is valid.
D 2.1: acknowledgement bit, read curve values channel 13
This bit is set by FB 162 when the read function is complete and the values have
been stored in data block DB-B. This bit remains set until a new job is started.
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IP244
C79000–B8576–C861–02