Siemens SINUMERIK 840Di Function Manual page 564

Detailed Description
2.5 Block search
Action blocks
Action blocks contain the actions accumulated during "Block search with calculation", such
as auxiliary function outputs and tool (T, D), spindle (S), and feedrate programming
commands. During "Block search with calculation" (contour or block end point), actions such
as M function outputs are accumulated in socalled action blocks. These blocks are output on
an NC Start after "Search target found".
Note
With the action blocks, the accumulated spindle programming (S value, M3/M4/M5/M19,
SPOS) also becomes active.
The PLC user program must ensure that the tool can be operated and that, if necessary, the
spindle programming is reset via PLC signal:
DB31, ... DBX2.2(spindle reset)
or the spindle programming is not output.
Single-block processing: MD10702 $MN_IGNORE_SINGLEBLOCK_MASK ()
By setting bit 3 = 1, it is possible to prevent a stop after every action block in singleblock
mode.
Boundary conditions for approach block/target block
Block search type 2
Interface signal:
DB21, ... DBX32.4 (approach block active)
is only set with "Block search with calculation at contour" because a separate approach
block is not generated with "Block search with calculation at block end point" (the approach
block is the same as the target block).
Block search type 4
The approach movement "Search with calculation to block end point" is performed using the
type of interpolation valid in the target block. This should be G0 or G1, as appropriate. With
other types of interpolation, the approach movement can be aborted with an alarm (e.g.
circle end point error on G2/G3).
ASUB after and during block search
If an ASUB is started after "Block search with calculation", the positions in the interpreter are
synchronized with this operation. $P_EP returns the position at which the axes are actually
located to the ASUB.
The collective block search position can be scanned via system variable $AC_RETPOINT.
This variable supplies the position as a non modulo-converted position, and an existing
rotation count can be lost.
2-28
Mode Group, Channel, Program Operation, Reset Response (K1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0