Yaskawa MotionWorks IEC - Manual (Page 35)

PLCopenPlus Function Blocks for Motion Control 2013-04-13 27
Rules for the definition of Motion Control function blocks
according to PLCopen
The input/output variables of the function blocks mandatory according to
the PLCopen Standard are marked with the letter 'B' in the defined tables
in the definition of the function blocks.
Input/output variables marked with the letter 'E' are optional, i.e. they can
be implemented but are not mandatory.
Vendor specific input / output variables, i.e. added by the vendor, are
marked with the letter 'V'.
According to the IEC 61131-3 specification, the input variables may be
unconnected or not parameterized by the user. In this case, the function
block will use the value from the previous invocation of the function block
instance, or in case of the first invocation, the initial value will be used.