Siemens SIMATIC S5 Manual page 220

To ensure that the signal edge evaluation is effective, the selected mode must remain active in
the function block until the traversing movement is complete. The command bits should, how-
ever, be reset as quickly as possible.
If there is a power failure while a command bit is set and if, after the return of power the same
command must be sent with a cold restart in the first PC cycle, this is not possible because the
edge flag in the binary identifiers in the axis DB is still set to /1/, The FB therefore considers that
the job has already been started.
Once a job has been triggered, it is sent to the positioning module immediately when the func-
tion block FBI 64 is next called.
A job is only automatically repeated when a parameter assignment error in the SEND data hand-
ling block is signalled.
As soon as a valid monitoring job (BA = 71, 73) is recognized, it is executed at each JU FBI 64
call, providing there is no operating job in the call.
Mode 74 interrupts the cyclic monitoring. The monitoring function is resumed when one of the
modes BA 71, or 73 is transferred.
The information read is written to the axis data block as follows: (with parameter DWNR = n):
DW n+9 and DW n+10 :
The output at parameter ANZG (ANZ1 and ANZ2 with theS5-115U) or in the axis data block is in
binary in fixed point double word format (32 bits).
.
with indirect parameter assignment: when data byte DR7 of the open DB has the value
The output is as a seven digit BCD number with sign
— with indirect parameter assignment: when data byte DR7 of the open DB is not equal to
exceeded), the content of the parameter ANZG (ANZ1 and ANZ2 with the S5-1 15U) is un-
changed with direct parameter assignment. If the representable BCD numerical range is
exceeded with indirect parameter assignment, the monitoring value is stored as a 32-bit fixed
point number (2's complement) in the axis data block.
The positioning module IP247 does not service interrupts.
With indirect parameter assignment, the current data block (DB or DX) must be open and must
have values supplied before function block FBI 64 is called.
The Standard Function Block FB164
actual position value, binary or BCD
free
distance to go, binary or BCD
6 - 2 7