EVENT PHASE MODULATOR FOR INTEGRATED CIRCUIT TESTER

摘要

A drive circuit (40) for an integrated circuit tester produces an output test signal in response to an input sequence of vector data values, wherein each vector data value references a test signal state and a time at which the test signal is to change to the reference state. The drive circuit includes decoding and timing circuits for producing an indicating signal (D) of the state referenced by each incoming vector data value and a timing signal (TD) having a pulse occurring at the time referenced by the incoming vector data value. An event phase modulator (46) within the drive circuit stores a control bit indicating the state of the indicating signal in response to each pulse of the timing signal. The event phase modulator waits for a variable amount of time after storing each control bit and then forwards the control bit to the input of a driver (42) producing the test signal. The driver sets the test signal state in accordance with the state of the control bit. The delay between the time the event phase modulator stores a control bit and forwards it to the driver is a function of time determined by input programming data. Thus the event phase modulator phase modulates the test signal in a manner determined by its input programming data.