ALLOW bits activate a command on the falling edge of the bit (changing from state 1 to state 0). It has a disallowing action while the bit is at state 0. When the ALLOW bit changes from state 0 to state 1, this removes the inhibiting action and allows the associated commands.

Presymbolization of the ALLOW bits begins with ALLOW_ (see Language Objects and IODDTs Associated Specifically with the SERCOS Module).

NOTE: ALLOW bits are initialized at state 1.

CONTROL bits activate a command on the rising edge of the bit. The command is issued; it will have effect if the MovementSet is in a state, which allows the command to be carried out. You must therefore check the MovementStatus of the MovementSet before activating a command. CONTROL bits have a corresponding ALLOW bit. One common reasons for the inability of a CONTROL to activate a command stems from the fact that the ALLOW bit associated to this command or the SERCOS® channel has the value 0.

CONTROL bit names begin with CONTROL_ (see Language Objects and IODDTs Associated Specifically with the SERCOS Module).

The pulse period must be greater than the module cycle time (default Cycle_time = 4 ms), so that the command is "seen" by the module.