Patent ID: 8829932

Claim:
A mobile electronic device comprising: a processor; an accessory port; and an accessory interface circuit coupled to the processor and the accessory port, the accessory interface circuit including: a test mode interface circuit, the test mode interface circuit including: a voltage comparator configured compare a first voltage to a second voltage; a ripple counter configured to count pulses from the processor when the voltage comparator indicates that the first voltage is greater than the second voltage; wherein the test mode interface circuit is configured to provide a test mode enable signal and an indication of a desired test mode of a plurality of test modes of the accessory interface circuit; and wherein the indication includes each state of a plurality of bits of the ripple counter; a detection terminal coupled to a terminal of the processor; an enable input coupled to an output of the processor; and wherein the accessory interface circuit, in response to the test enable signal from the test mode interface circuit and a first bit pattern indicative of the desired test mode, is configured to receive a detection override signal from the processor and to provide an output of a microphone comparator to a Send/End output of the interface circuit, wherein the microphone comparator is coupled to a microphone input of the accessory port.