Supplementary Conditions; Examples; Writing To Plc-I/Os - Siemens SINUMERIK 840D sl Function Manual

2.3.3

Supplementary conditions

Several slots
If several slots form an input or output range of the PLC I/O used directly by the NC, the address
range of the slots must be configured as a continuous range without gaps.
Parallel writing of the NC and PLC
Parallel writing of I/O outputs by the NC via direct access over the PLC and from the PLC user
program results in a random, mutual overwriting of the output values. The application is
therefore not permitted, but cannot be prevented on the control.
Time response
The time when the data is read in from the PLC I/Os is not synchronized with the time when
the data is made available to the part program via system variables!
Data transfer
● The output of the output data on the PLC I/O is always for all parameterized output data,
even when only one output data item was written for each system variable.
● If several system variables are assigned values simultaneously, it is not certain that they
are transferred in the same interpolation cycle.
2.3.4

Examples

2.3.4.1

Writing to PLC-I/Os

Specifications
● Decimal logical addresses of the output data to be written within the PLC I/O
– 521: 1-byte integer value
– 522: 2-byte integer value
● The output data is written to a part program via the R parameters R10 - R11.
● In order to only slow down the execution of the PLC user program (OB1) slightly, the update
cycle for write access should be 3-times the interpolator cycle of 12 ms.
● Data is to be output directly to the following PLC I/Os:
Parameterization
The machine data should be set as follows:
● Length of the NC I/O output data area: 2 + 1 = 3 bytes
MD10396 $MN_PLCIO_NUM_BYTES_OUT= 3
● Logical start address of the input data area: 521
MD10397 $MN_PLCIO_LOGIC_ADDRESS_OUT = 521
Extended Functions
Function Manual, 10/2015, 6FC5397-1BP40-5BA3
A4: Digital and analog NC I/O for SINUMERIK 840D sl
2.3 Direct I/O access via PLC
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