Plc Machine Data - Siemens SINUMERIK 828D Function Manual

P3: Basic PLC Program for SINUMERIK 840D sl
13.8 Structure and functions of the basic program
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).
13.8.10

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 sizes of the individual areas, and hence the total length of the DB 20, is set by the following PLC machine
data:
MD14504 $MN_MAXNUM_USER_DATA_INT
MD14506 $MN_MAXNUM_USER_DATA_HEX
MD14508 $MN_MAXNUM_USER_DATA_FLOAT
These settings are 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:
1. Integer-MD
2. Hexa-fields MD
3. 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 Functions
890
Function Manual, 09/2011, 6FC5397-0BP40-2BA0