Rockwell Automation 2711 PANELBUILDER SOFTWARE USER MANUAL - Manual (Page 367)

PLC Programming Considerations
Appendix A
A-3
When in the “scanner mode” the PLC-5/15 can block transfer to and from
connected PanelView terminals, as well as intelligent I/O modules in
remote I/O racks. The PLC-5/15 processor allows block transfers to be set
for either “non-continuous” or “continuous” operation. Refer to the
PLC-5/15 Processor User’s Manual for complete details.
IMPORTANT: For PLC-5/15 block transfers to function properly, you
must use a PLC-5/15 Series B, rev. J or later.
NonĆContinuous" Block Transfer Mode
In this case, each time the block transfer instructions are complete, they are
re-enabled when the next program scan occurs. The program scan time is
normally short enough that block transfer timing will be more than
adequate. This method guarantees that the order of queuing follows the
order scanned in the PLC program.
If the PLC-5/15 program requests more than one transfer to and from the
same I/O chassis (or terminal) in the same program scan, the requests are
placed in queue (up to 17 requests per chassis) and executed in the order
requested.
Your PLC program should condition the use of block transfer data on
examination of the block transfer error bit. An error may occur when the
processor is switched from run mode, or when processor communications
are interrupted by excessive electrical noise or by disconnection of the
remote I/O cable.
BiĆDirectional Block Transfer Example
(PLCĆ5/15)
Figure A.1 shows the recommended PLC programming for bi-directional
block transfer communication with a PanelView terminal. The following
programming method will continually execute bi-directional block
transfers as quickly as the program and I/O scan allows in the
non-continuous mode.
PLCĆ5/15 Block Transfer
Programming Examples