Fifo Variables ($Ac_Fifo1[N] - Siemens SINUMERIK 840D sl Programming Manual

Motion synchronous actions
10.3 Main run variables for synchronized actions
10.3.10 FIFO variables ($AC_FIFO1[n] ... $AC_FIFO10[n])
Function
10 FIFO variables (circulating buffer store) are available to store associated data sequences.
Data type: REAL
Application:
● Cyclical measurement
● Pass execution
Each element can be accessed in read or write
FIFO variables
The number of available FIFO variables is defined in machine data
MD28260 $MC_NUM_AC_FIFO.
The number of values that can be written into a FIFO variable is defined using machine data
MD28264 $MC_LEN_AC_FIFO. All FIFO variables are equal in length.
The sum of all FIFO elements is only generated if bit 0 is set in
MD28266 $MC_MODE_AC_FIFO.
Indices 0 to 5 have a special significance:
Index
0
1
2
3
4
5
6 to n
658
Significance
While writing:
While reading:
Access to oldest stored element
Access to latest stored element
Sum of all FIFO elements
Number of elements available in FIFO.
Read and write access can be assigned to each element of the FIFO. FIFO
variables are reset by resetting the number of elements, e.g. for the first FIFO
variable: $AC_FIFO1[4]=0
Current write index relative to beginning of FIFO
Access to nth FIFO element
max
New value is saved in the FIFO.
The oldest element is read and removed from the FIFO.
Programming Manual, 06/2009, 6FC5398-2BP20-0BA0
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