ProSoft Technology MVI69-DFCM User Manual page 54

Ladder Logic
When the DFCM.BlockRequest.EventCommandP1 bit is set, the rung will execute. It will
place the command contained in the rung in the command queue for execution. This
technique can be used to issue commands on a port without constructing a master
command list or to execute commands that are to be issued under special conditions.
If the module is configured for no or only one block transfer, special processing is
required. The module must observe the first word of the module's output image changing
in order to recognize the receipt of new data. If the value never changes, the module will
not process the data. This presents a problem when fewer than two blocks are to be
48 ProSoft Technology, Inc.
MVI69-DFCM User Manual
June 24, 2004