A programmable logic integrated circuit device adapted to enter a
low-power mode is described. The integrated circuit device includes a
programmable logic block, a first low-power mode control circuit
programmed into a portion of the programmable logic block, a second
low-power mode control circuit, and a low-power enable input coupled to
the first low-power mode control circuit and the second low-power mode
control circuit. This arrangement allows the programmable logic
integrated circuit device to transition into and out of low-power mode in
response to a single signal from system control logic, so that the system
control logic can be designed without detailed understanding of the inner
workings of the programmable logic integrated circuit device or its
programmed design.