| 摘要 |
PURPOSE:To decrease the capacity of a microprogram memory, by enabling to select a register designated with a microinstruction through a register designation field of the said instruction without increasing the length of a microinstruction word. CONSTITUTION:A register designation field (r) of a microinstruction entried in a microinstruction register 11 is taken as 3-bit. In case of r=(1,0,0), when an X register is designated, a logic of a gate 40 is established and an output 4d becomes 1. Thus, address signals 4a and 4e is reduced to 0. When the content I of a macroinstruction register is taken as I7=1, I5=1 and I1=1 and register B is designated, a signal 4g is 1 and a signal 4f is 1, the content of (r) is changed to (0,0,1) and the register B is selected. In case of the rnot equal to (1,0,0), the output 4d of the gate 40 is 0, and similarly, the (r) field of the micro-instruction register is a register address as it is. |
