ONE-CHIP MICROCOMPUTER

摘要

PURPOSE:To obtain an one-chip microcomputer saving the number of instruction steps and execution time by providing the 1st and 2nd adders and a constant generating circuit. CONSTITUTION:Two 4-bit inputs to a 4-bit binary adder 1 are 10-A3, B0-B3 respectively and a carrying input 1a selects a binary carrying signal 5a and a decimal carrying signal 6a by a carry selecting gate 4. The added results of an adder 8 are outputted as 4-bit added result outputs C0-C3 and a carrying output signal 1b. A constant circuit 3 inputs a carrying signal 1b, added results C1- C3 and control signals 3a, 3b and outputs constant outputs D1-D3 and a decimal carrying signal 3c. An adder 2 inputs added results C0-C3 outputted from the adder 1 and constant outputs D1-D3 of the constant generating circuit 3 and outputs binary-coded decimal outputs E0-E3 of the added results.