Microcomputer with built in debugging capability

A debug instruction program is executed to enable a latch contents setting register to select the address of a specified part of a memory to be monitored. The selected address is given to a latch timing controller 18, and the internal state of the specified part of memory is supplied to a display contents latch unit according to information from an address bus and a bus timing control signal. The display contents latch unit latches the internal state and supplies it to a display device so that the internal state of memory can be identified and debugged.