Abstract: A circuit is disclosed which is implemented on the same silicon chip as a microprocessor to be utilized in a microprocessor system such as a microcontroller, which circuit allows a user to perform in-circuit emulation ("ICE") for the purpose of debugging the microprocessor system. The ICE circuitry comprises (i) capture logic which monitors the contents of the program address register and the internal data bus and various control lines of the processor; (ii) trace circuitry comprising a FIFO buffer which puts data from the capture logic to the output pins of the chip; and (iii) a content addressable memory and a software programmable logic array with emulation counters which together function as a finite state machine which performs the desired predetermined testing of the system.