Sleep3 ... MicroBlaze is in sleep mode after executing a SLEEP instruction or by setting Reset_Mode[0:1] to 10, all external accesses are completed, and the pipeline is halted
When an MBAR instruction is executed to enter sleep mode and MicroBlaze has completed all external accesses, the pipeline is halted and either the Sleep, Hibernate, or Suspend output signal is set.
It seems that in this architecture, the functionality you're calling may be referring to a sleep mode, and not a "don't do anything for X amount of time" function. But I am only guessing.