Siemens SINUMERIK 840D sl Function Manual page 1337

Structure of FB 1 in the OB100
(enter the number of M groups to be decoded in order to activate the function):
Call FB 1, DB 7(
...
ListMDecGrp := 3,// M decoding of three groups
....
);
The appending of the entry in OB 100 and transfer of DB 75 (decoding list) to the AG must
be followed by a restart. During the restart, the basic program sets up DB76 (signal list).
If the NC program is started at this point and the expanded M function (e.g., M3=17) is
processed by the NCK, this M function will be decoded and bit 2.5 set in DB 76 (see
decoding list DB 75). At the same time, the basic program sets the read-in disable and the
processing of the NC program is halted (in the corresponding NC-channel DB the entry
"expanded address M function" and "M function no." is made).
The readin disable in the channel is reset once the user has reset and, therefore,
acknowledged, all the bits output by this channel in the signal list (DB 76).
2.7.10 PLC machine data
General
The user has the option of storing PLCspecific machine data in the NCK. The user can then
process these machine data after the power-up of the PLC (OB 100). This enables, for
example, user options, machine expansion levels, machine configurations, etc., to be
implemented.
The interface for reading these data lies in the DB 20. However, DB20 is set up by the basic
program during powerup only when user machine data are used i.e. sum of GP parameters
"UDInt", "UDHex" and "UDReal" is greater than zero.
The size of the individual areas and thus also the total length of DB20
is set by PLC machine data:
MD14504 MAXNUM_USER_DATA_INT
MD14506 MAXNUM_USER_DATA_HEX
MD14508 MAXNUM_USER_DATA_FLOAT
is set and specified to the user in the GP parameters:
"UDInt", "UDHex" and "UDReal"
.
The data is stored in the DB 20 by the BP in the sequence:
Integer-MD, Hexa-Fields-MD, Real-MD.
The integer and real values are stored in DB 20 in S7 format.
Hexadecimal data are stored in DB20 in the order in which they are input (use as bit fields).
Basic logic functions: PLC basic program solution line (P3 sl)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
2.7 Structure and functions of the basic program
Detailed description
63