| 摘要 |
PURPOSE:To improve the degree of freedom of branching, by splitting a program counter into a lower-order counter section and a higher-order counter section and modifying the higher-order counter section into a value corresponding to a relative position from a small block existing in an instruction word. CONSTITUTION:When an instruction code is decoded as a relative page branch instruction, an address section 11 of a program counter selects the address section of an instruction code from a transmission line 21 at a selecting circuit 18 from the disconnection of the output of the switching signal 26 and an adder 15 and gives an output to a latch circuit 17-1. A control signal 24 is outputted by the +1 operation wth a part indicating +1, 0, -1 of a page section of an instruction code, and an AND gate 16 goes to 1. Only the page section is added by +1 with an adder/subtractor 14 together with the output of an addition/ subtraction controlling signal 23 and an output is given to a latch circuit 17-2. In case of the -1 opration, the signal 23 commands similarly the subtraction, and in case of 0 operation, the signal 24 controls the output of the AND gate 16 to 0 for addition/subtraction. |
