Switchover Modes For Dryrun And Skip Levels - Siemens Sinumerik 802D sl Programming Manual

04.07
4.6.4

Switchover modes for DryRun and skip levels

Switching over the skip levels (DB21 DBB2) always constitutes an intervention in
the program run, resulting in a brief drop in velocity along the path in earlier SW
versions. The same applies to the switchover of DryRun mode (DryRun = dry run
feedrate DB21.DBB0.BIT6) from DryRunOff to DryRunOn or vice versa.
With a new switchover mode that has limited functionality, it is now possible to
avoid the drop in velocity.
By setting machine data $MN_SLASH_MASK==2, it is no longer necessary to re-
duce the velocity when the skip levels are switched (i.e. a new value in the
PLC-->NCK Chan interface DB21.DBB2).
Notice
The NCK processes blocks in two stages, the preprocessing and main runs. The
result of the preprocessing run is transferred to the preprocessing memory from
where the main run fetches the oldest block in each case and traverses its geome-
try.
Attention
When you set machine data $MN_SLASH_MASK==2, the preprocessing run is
switched over when the skip levels are changed! All blocks stored in the prepro-
cessing memory are traversed with the old skip level. As the user, you generally
have no control over the fill level of the preprocessing memory. From your viewpo-
int, therefore, the new skip level will become operative "at some point" after the
levels are switched!
Notice
Part program command STOPRE clears the preprocessing memory. If you switch
the skip level over before the STOPRE command, all blocks after the command
will be reliably changed over. The same applies to an implicit STOPRE.
Switching over DryRun mode is subject to analogous restrictions.
If you set machine data $MN_DRYRUN_MASK==2, no drop in velocity will be ne-
cessary when you change over the DryRun mode. In this instance as well, howe-
ver, it is only the preprocessing run that is switched over, resulting in the restric-
tions described above. In other words: Watch out! DryRun mode will become
active "at some time" after it has been switched over!
© SIEMENS AG 2007 All rights reserved
SINUMERIK 802D sl/840D sl840D/840Di sl/840Di/810D ISO Turning -- 04.07 Edition
Enhanced Level Commands
4.6 Advanced functions
4-151