Importance

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Abstract

A start-stop synchronous communication speed detecting apparatus includes a counter, a speed determining unit, a clock switching unit, a shift register, a character determining unit, a code generator, and a controller. The counter counts a time period, in which received data is a space polarity, in start-stop synchronous communication. The speed determining unit compares the count value with a time per bit of a specified communication speed. The clock switching unit selects a clock synchronized with the start bit of the received data and having the same frequency as that of the specified communication speed. The shift register stores the received data. The character determining unit compares a received character from the register with a predetermined character. The code generator supplies codes of the first to Nth characters to the character determining unit. The controller counts received characters by the output clocks from the switching unit and informs the generator of the number of characters, generates a reception completion information signal upon receiving a predetermined character string without any abnormality, and outputs a signal for initializing the counter by a signal indicating abnormality in the speed and character determining units.

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First Claim