Rockwell Automation GMLC Reference Manual - Manual (Page 407)

Publication GMLC-5.2 - November 1999
370 RIO Blocks
On RIO blocks, with Wait for RIO Block Transfer selected, are not
usually required unless block transfers to and from the PLC must be
synchronized to the program in the motion controller (generated from the
GML Commander diagram). More commonly, the motion controller
program must be synchronized to the PLC program. In this case, it is
easier to use discrete bits to synchronize and interlock block transfers in
the PLC program.
If other tasks are executing (multitasking), the task that contains this
block pauses while the other tasks continue to execute. In this way, a Wait
for RIO Block Transfer selection in one task does not pause execution of
any other tasks or hang the task dispatcher.
If RIO Block Transfer
Use the If RIO Block Transfer selection to evaluate whether a block
transfer read or write from the RIO scanner has occurred.
Program flow branches to the top (true) node if the selected type of block
transfer has occurred, and to the bottom (false) node if not.
Use On RIO blocks, with If RIO Transfer selected, to check for an RIO
fault. For both block writes and block reads, the condition is true only
once immediately after the appropriate block transfer has been completed.
On RIO blocks, with If RIO Block Transfer selected, are not usually
required unless block transfers to and from the PLC must be synchronized
to the program in the motion controller (generated from the GML
Commander diagram). More commonly, the motion controller program
must be synchronized to the PLC program. In this case, it is easier to use
discrete bits to synchronize and interlock block transfers in the PLC
program.