| 摘要 |
PURPOSE:To perform high-speed, high-precision arithmetic through a small-scale circuit by selecting which of the outputs of a binary arithmetic circuit and a correcting circuit making the binary-coded decimal correction of the output signal of the binary arithmetic circuit is selected on the basis of a microcode. CONSTITUTION:When a microcode for setting a binary arithmetic mode is stored in a program memory 6 and executed, an instruction decoder 7 outputs a control signal which selects not the output of the decimal correction circuit 7, but the output of the binary arithmetic circuit 3 to a selecting circuit 5 and the output of the binary arithmetic circuit 3, i.e. the binary arithmetic results of a temporary register 1 and a temporary register 2 are outputted to a data bus 8. Consequently, this is effective for all or specific arithmetic instructions until a microcode which changes the setting to the decimal arithmetic mode is executed newly. |
