Patent ID: 8705687

Claim:
An input circuit in high speed counter module for programmable logic controller (PLC) configured to input a pulse to an micro-processor unit (MPU), the input circuit comprising: a first multi-vibrator generating a pulse by detecting rising and falling edges of a first contact input; a second multi-vibrator generating a pulse by detecting rising and falling edges of a second contact input; a first buffer outputting an output of the first multi-vibrator in 3-state; a second buffer outputting an output of the second multi-vibrator in 3-state; a first multiplexer (MUX) outputting any one of an EX-OR signal of the first and second contact inputs and a reverse signal of the EX-OR signal; a second MUX outputting any one of an output of the first MUX and the second contact input; and a first switch outputting outputs of the first and second buffers as a first phase input or a second phase input.