Siemens SINUMERIK 840D sl Function Manual page 1044

Detailed description
2.7 Structure and functions of the basic program
Description
Abbreviated symbolic names of the interface signals are defined in the two STL files
NST_UDT.AWL and TM_UDT.AWL.
In order to create the reference to the names of the interface signals, the name is included in
the comment after each signal.
The symbolic names, commands and absolute addresses can be viewed by means of a
STEP 7 editor command when the UDT block is opened.
Note
Unused bits and bytes are listed, for example, with the designation "f56_3".
"56": Byte address of the relevant data block
"3": Bit number in this byte
2.7.9 M decoding acc. to list
Description of functions
When the M decoding according to list function is activated via the GP parameter of
FB1 "ListMDecGrp" (number of M groups for decoding), up to 256 M functions with extended
address can be decoded by the basic program.
The assignment of the M function with extended address and the bit to be set in the signal
list is defined in the decoding list. The signals are grouped for this purpose.
The signal list contains 16 groups with 16 bits each as decoded signals.
There is only one decoding list and one signal list i.e. this is a cross-channel function.
The M functions are decoded. Once they are entered in the decoding list, then the
associated bit in the signal list is set.
When the bit is set in the signal list, the readin disable in the associated NCK channel is set
simultaneously by the basic program.
The readin disable in the channel is reset once the user has reset all the bits output by this
channel and thus acknowledged them.
The output of an M function decoded in the list as a highspeed auxiliary function does not
result in a readin disable.
The figure below shows the structure of the M decoding according to list:
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Basic logic functions: PLC Basic program powerline (P3 pl)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0