| 摘要 |
PURPOSE:To reduce the number of steps of a microprogram, to shorten execution time and to save the capacity of a memory by forming a zero deciding circuit in a register and permitting/unpermitting a register write signal to the register on the basis of the decided result. CONSTITUTION:When an instruction is started, a mask value is written in a register B2 and the contents of registers A1-A7 are written. When data are set up in the register A1, a zero detecting circuit 3 judges the zero value of the data and informs the judged result to a writing control part 4. At that time, the circuit 3 judges the zero value of the register A1 on the basis of bit length specified by a bit length latch 5. When a signal line 14 indicates a zero value, the control part 4 sends a validated register write signal 11 to enable the succeeding writing, and when indicating a non-zero value, inhibits the writing. At the execution of operation or the generation of a setting instruction, the register write signal can be using a signal line 15 and resetting the control part 4.
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