Block Search From Last Main Block - Siemens sinumerik 840D sl Function Manual

2. NC START for output of approach block
For more information, see the signal chart for "NC START rejected with alarm" in Figure
"Signal chart", Subsection "Functional sequence".
2.5.4

Block search from last main block

Meaning
As mentioned above, a block search with calculation on contour is carried out as part of
retrace support. Even if the most powerful NCUs are used, this can lead to computing times
of several minutes for very large part programs until the target block is reached. This delay
time can be significantly reduced by using the block search from last main block.
Functionality
For retrace support with block search from the last main block, the search for the target block
takes place in 2 stages:
1. Block search without calculation from start of machining program to last main block
2. Block search with calculation on contour from main block to target block. This block
Requirements
To enable a search from last main block for retrace support, at least one main block must be
programmed after the RESU start CC_PREPRE(1).
Main block
All instructions required for processing the subsequent section of the part program must be
programmed in one main block.
Main blocks must be identified by a main block number consisting of the character ":" and a
positive integer (block number).
A complete description of how to use main blocks appears in:
References:
/PG/ Programming Fundamentals Manual; Fundamentals of NC Programming, Language
Elements of the Programming Language
Special functions: Retrace Support (TE7)
Function Manual, 11/2006, 6FC5397-2BP10-2BA0
The RESU ASUB CC_RESU_BS_ASUP must be completed. Interface signal:
DB21, ... DBX318.0 == 1 (ASUB stopped)
before target block. Subroutines are ignored during this search, i.e. it takes place
exclusively in the main program.
search does not ignore subroutines.
Detailed description
2.5 Retrace support
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