In one embodiment of the invention, a programmable logic device, such as an FPGA, has programmable I/O circuits that can be programmed into any one of a number of different operating modes before configuration is completed. As such, the same set of I/O circuits and corresponding I/O pads can be used to configure the device using different configuration interfaces having different interface signaling requirements. Such a device may be able to be implemented using fewer I/O pads than conventional devices that employ a different set of I/O pads for each different type of configuration interface supported by the device.