Trace method and apparatus for use in a data processing system

摘要

A data processing system includes means which are operative when the system is conditioned for operating in a trace mode during the processing of program instructions, to record the op code of each instruction designated as executable by the bit contents of a table referenced before beginning instruction execution. When the op code of an instruction is designated by the table as not being executable, the system traps the instruction and generates a call to the operating system software without recording its op code. The selective recording and trapping of instruction operation codes facilitates diagnosis of program errors or faults within the system. This is particularly valuable when the system includes emulation apparatus which may not be completely compatible in every detail with the system being emulated.