Siemens SIMATIC FM 353 Manual page 233

Block advance
The program is prepared up to the end point of the target block; the tool offset, M
commands and dwell times are output; and the traversing movements are sup-
pressed.
When processing traversing programs with a forward block search, there are a
number of special cases:
S The external forward block search (G50) is not executed.
S Continuous travel with functions to set (G88, 89) or delete (G87) an actual
value on-the-fly is not executed.
S The blocks under G50, G87, G88, G89 (in the processing direction) should con-
tain a path in absolute coordinates.
Block return
Similar to block advance
Automatic block advance/return
Automatic block advance/return means that, after the interruption of an active auto-
matic program (by an operating mode change), you can continue execution from
this point of interruption in the appropriate direction of processing.
With forward block search, the interrupted program must previously have been go-
ing in the forward direction.
With block search in reverse, the interrupted program must previously have been
going in the reverse direction.
The command for automatic forward or reverse block search is evaluated in the
FM 353 at Start, and a forward or reverse block search to the interruption point is
executed in the "Jog" mode at the velocity of stage 1. Positioning to the interruption
point takes place (if positioning has taken place previously in some other mode),
and then the interrupted block is processed, including any required output.
Control actions
Prerequisites:
S The FM 353 has been inititalized.
S The mode has been selected and acknowledged.
S Drive Enable [AF] is = 1 (control signal in user DB, DBX15.7)
S Stop [STP] is = 0 (control signal in user DB, DBX15.1)
S Servo Enable (RF) is = 1 (user DB, DBX34.0)
S Axis is synchronized.
FM 353 Stepper Drive Positioning Module
6ES7 353-1AH01-8BG0
Description of Functions
9-33