| 摘要 |
<p>PURPOSE:To make it possible to effectively change the flow of the instruction execution of a CPU from the outside of the CPU. CONSTITUTION:The PC register 12 of a program counter 10 holds an address value used for the address designation when a program instruction is read. A PC output buffer 18 outputs the address value of the PC register 12 to an address bus BA when 'without change' is inputted from a PC value change signal SPC. When 'with change' is inputted, the output to the address bus BA becomes a high impedance state. An adder 22 performs an increment not for the address value that the PC register 12 outputs and but for the address value to be inputted from the address BA in the case of 'with change' and writes this result in the PC register 12.</p> |
