Rockwell Automation 1771-QA Stepper Positioning Assembly User Manual - Manual (Page 54)

3–32 Programming and Operation
Publication 1771-UM002A–EN–P – May 2000
B. Setting the skip bit in the single move control words
corresponding to unwanted move blocks. Program logic can
be used to set bit 02 in the 59th, 53rd, 47th word, etc. of the
write block transfer file so that respectively the last, next to
last, third from last, etc. move blocks of a moveset are
skipped by the stepper controller module.
C. Programming the block transfers of multiple movesets so that
each moveset is the same size or larger than the previous one.
It will be necessary to clear the write block transfer file after
the last moveset has been transferred in order to start the
sequence again.
Programming Commands
When a command is transferred to the stepper controller module, the
transfer will contain either one word or four words of new data. This
will depend on whether the moveset control word (MCW) alone, or
the moveset control word, offset, and preset words are moved into
the write block transfer file just prior to the transfer. Moveset data
that remained in the write block transfer file from a previous transfer
will accompany the command data. This unwanted moveset data
may or may not have to be voided depending upon which command
bit is set.
Start MCW, bit 00
Usually accompanied by the first moveset after a reset or stop
command, or after a profile has ended. The first moveset could have
been previously transferred without the start command. If so, the
stepper controller would process the data accompanying the
command, load it into the working or storage area (writing over any
previously loaded data) and execute the start of the moveset.
Reset and Stop MCW, bits 04 and 06
The stepper controller module clears all moveset data in both the
working and storage areas and ignores all accompanying data when
it receives a reset or stop command.
Offset MCW, bit 13
A block of four words is required to transfer an offset command with
data (preset words must be included even if unused). The moveset
data (unwanted) accompanying the offset command will be
processed by the stepper controller module.
Choose one of the methods for voiding unwanted data described in
“Block Length,” above.