Siemens SIMATIC FM 353 Manual page 232

Description of Functions
User DB allocation
Data format
Byte 0
Byte 1
Byte 2
Forward processing
The program processes the block numbers in ascending order.
Processing begins at Start, with the first block (specified block number = 0).
If processing is to begin at some other point of the traversing program, specify the
desired block number.
Processing will take place by searching forward to this block, then processing for-
ward until the program end command is recognized.
Backward processing
The program processes the block numbers in descending order.
Processing begins at Start, with the last block (specified block number = 0).
If processing is to begin at some other point of the traversing program, specify the
desired block number. Processing will take place by searching back to this block,
then processing in reverse until the program beginning is recognized.
Note
If reverse processing is to execute the same sequence of movements as the for-
ward movement, the effects of the corresponding commands must be taken into
account in the programming. For example:
S
M outputs should be written separately in a block;
note M output (MD32) and G60/G64.
S
Note change between G60/G64 and G90/G91.
S
Note start and end of tool offsets.
S
M18 is not executed.
S
M02 and M30 at the end of the program are not processed.
9-32
Program number
Block number
Direction of machining: 0 = process forward
1 = process in reverse
Significance
FM 353 Stepper Drive Positioning Module
6ES7 353-1AH01-8BG0