Data processing apparatus with self-emulation capability

Abstract

A microprocessor, specially adapted for graphics processing applications, and which has a self-emulation capability by which the contents of its internal registers may be dumped or loaded to or from external memory on an instruction-by-instruction basis, is disclosed. The microprocessor has circuitry which is responsive to an emulate enable signal, or to a predetermined instruction code, so that normal execution is halted at the end of the ion, with execution jumping to a predetermined vector. Responsive to a dump signal, the microprocessor begins execution of a routine which presents a predetermined series of memory addresses on a memory bus, in conjunction with the contents of registers internal to the microprocessor. Accordingly, the addressed locations of a memory device connected to the memory bus can be written with the register contents, for subsequent interrogation by the user. Similarly, responsive instead to a load command, a routine is executed which presents the series of addresses to the memory bus and loads the internal registers with the data values presented on the memory bus. The load feature is similarly utilized by the user's loading of the addressed memory locations with the desired contents of the internal registers. A system containing a microprocessor constructed according to the invention may be configured so that the emulate enable signal is generated by the control signals generated by the microprocessor upon each instruction fetch from the external memory.