Siemens SINUMERIK 840D sl Programming Manual page 468

Path traversing behavior
10.6 Program sequence with preprocessing memory (STOPFIFO, STARTFIFO, FIFOCTRL, STOPRE)
Meaning
STOPFIFO
STARTFIFO
FIFOCTRL
STOPRE
Note
The preprocessing memory is not filled or filling is interrupted if the machining step contains
commands that require unbuffered operation (search for reference, measuring functions,
etc.).
Note
The control generates an internal preprocessing stop in the event of access to status data
($SA...).
Example: Stop preprocessing
Program code
...
N30 MEAW=1 G1 F1000 X100 Y100 Z50
N40 STOPRE
...
468
: identifies the start of a machining step to be buffered in the
STOPFIFO
preprocessing memory.
preprocessing memory until:

STARTFIFO
or
 The preprocessing memory is full
or
 The end of the program is reached
: starts rapid processing of the machining step; the preprocessing
STARTFIFO
memory is filled in parallel to this.
: Activation of automatic preprocessing memory control
: Stop preprocessing
stops processing and fills the
STOPFIFO
or is detected
STOPRE
Comment
; Measurement block with probe at first
measuring input and linear
interpolation.
; Preprocessing stop.
Programming Manual, 03/2013, 6FC5398-2BP40-3BA1
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