Specifies the mode configuration of the system bus
flow control FIFO threshold.
off -- the flow control FIFO threshold is set to the
original value defined by the system.
on -- the flow control FIFO threshold is set to the
lower value defined by the system.
auto -- the system starts monitoring the system bus
flow control FIFO threshold and will change the
flow control FIFO threshold from the original
value to the lower value when the system detects
the first occurrence of the threshold exceeding
on a physical entity (such as a module) over
the system allowed limit.