9/13/2005
Programming the SMLC
74
CoDeSys - Execute input vs. Enable input
•
All PLCopen motion control function blocks have either an
Execute input or an Enable input.
•
Execute inputs only trigger the action inside the function
block on the rising edge of the Execute input. Processing
inside the block continues until the function is complete and
the outputs are set. The outputs will remain set as long as
the Execute input remains TRUE. When the Execute input
is removed all outputs go off. If the Execute input is
removed before the internal processing of the block is
complete the outputs will be set for exactly one scan before
turning off.
•
Function blocks with Enable inputs will perform the process
inside the block as long as the Enable input is TRUE.
•
You might notice that in the EnableAxis function block we
have an input called Enable that feeds the Execute input of
the MC_Reset block. This is perfectly legitimate and merely
indicates that the Reset operation will only occur on the
rising edge of the Enable input to the block
