Abstract: A circuit for detecting timing errors and for selecting the correct clock edge for mid-point data sampling, includes a rising edge sampling device for sampling an input data signal at a rising edge of an input clock and generating a first interim data signal. A falling edge sampling device samples the input data signal at a falling edge of the input clock and generates a second interim data signal. An error signal generation devise, arranged in each of the rising edge and falling edge sampling devices, generates an error signal if designated setup time and hold time requirements are not met. The error signal is one of an error-rise or error-fall signal. A state machine receives the first and second interim signals and the error signal. The state machine automatically outputs the first interim data signal to a logic device if the error-fall signal is detected, and outputs the second interim data signal to the logic device if the error-rise signal is detected.

Abstract: In performing data communication between a subscriber terminal and a scanner of a remote information processing system, there is provided a data modulator-demodulator apparatus of a pseudo noise spread spectrum communication system for executing the data transmission and reception at a high speed, regardless of a voice speech use on a transmitting line. The transmitter part of the modulator-demodulator apparatus has a modulator which uses a pseudo noise code, generated by a pseudo noise code generator, to band spread real data, and the band spread data is converted to analog information by a transmitting converter for transmission over a transmitting line. The receiver part of the modulator-demodulator apparatus has a receiving converter which recovers operation clock data from the received analog signal, and converts a received analog signal to digital data. A demodulator in the receiver part then de-spreads the digital data in response to the pseudo noise code generated by the pseudo noise code generator.