Like described in the previous chapter, the input Execute triggers a new movement. With a rising edge of this input the values of the other function block inputs are defining the movement. Until version 1.1 of PLCopen there was the general rule that a later change in these input parameters does not affect the ongoing motion.

Nevertheless, there are numerous application examples, where a continuous change of the parameters is needed. The user could retrigger the input Execute of the function block, but this complicated the application.

Therefore, the input ContinuousUpdate has been introduced. It is an extended input to all applicable function blocks. If it is TRUE, when the function block is triggered (rising Execute), it will - as long as it stays TRUE – make the function block use the current values of the input variables and apply it to the ongoing movement. This does not influence the general behavior of the function block nor does it impact the single axis state diagram. In other words it only influences the ongoing movement and its impact ends as soon as the function block is no longer Busy or the input ContinuousUpdate is set to FALSE.

If ContinuousUpdate is FALSE with the rising edge of the input Execute, a change in the input parameters is ignored during the whole movement and the original behavior of previous versions is applicable. The ContinuousUpdate is not a retriggering of the input Execute of the function block. A retriggering of a function block which was previously aborted, stopped, or completed, would regain control on the axis and modify its single axis state diagram. Opposite to this, the ContinuousUpdate only effects an ongoing movement. Also, a ContinuousUpdate of relative inputs (e.g. Distance in MC_MoveRelative) always refers to the initial condition (at rising edge of Execute).