| 摘要 |
PURPOSE:To attain the confirmation of the circuit operation in a short time by providing an adder circuit receiving a count pulse, adding said count pulse or a carry pulse and generating a carry pulse goting to a high-order digit when the carry takes place so as to check the circuit without giving any change to all digits. CONSTITUTION:When a count pulse is inputted to an input terminal 11, it is ORed with a carry pulse 16a at an OR circuit 14 and added with an output addition value 17a of an N-bit shift register 17 at an adder circuit 15. An exclusive OR (EX-OR) circuit 152 of the adder circuit 15 makes addition and an AND circuit 151 discriminates the carry and outputs a carry pulse. The carry pulse is shifted by one bit at a 1-bit shift register 16 by using a serial conversion clock inputted from an input terminal 12 and fed back to the OR circuit 14 through a feedback circuit 16a. Further, the result of addition of the adder circuit 15 is inputted to the N-bit shift register 17, where it is subjected to N bit shift and fed back to the adder circuit 15 through the feedback circuit 17a after N-bit.
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