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Clock signal and legend. In electronics and especially synchronous digital circuits, a clock signal (historically also known as logic beat) [1] is an electronic logic signal (voltage or current) which oscillates between a high and a low state at a constant frequency and is used like a metronome to synchronize actions of digital circuits.
A clock generator is an electronic oscillator that produces a clock signal for use in synchronizing a circuit's operation. The output clock signal can range from a simple symmetrical square wave to more complex arrangements. The basic parts that all clock generators share are a resonant circuit and an amplifier.
The output of a flip-flop is constant until a pulse is applied to its "clock" input, upon which the input of the flip-flop is latched into its output. In a synchronous logic circuit, an electronic oscillator called the clock generates a string (sequence) of pulses, the "clock signal".
Pin 17 is the receiver clock (RCK), or receive timing (RT); the DTE reads the next bit from the receive data line (pin 3) when this clock transitions from ON to OFF. Alternatively, the DTE can provide a clock signal, called transmitter timing (TT, pin 24) for transmitted data.
SCLK CPOL=0 is a clock which idles at the logical low voltage. SCLK CPOL=1 is a clock which idles at the logical high voltage. CPHA represents the phase of each data bit's transmission cycle relative to SCLK. For CPHA=0: The first data bit is output immediately when CS activates. Subsequent bits are output when SCLK transitions to its idle ...
To send a byte of data back to the device, the host pulls Clock low, waits briefly, pulls Data low and releases the Clock line again. The device then generates a Clock signal while the host outputs a frame of bits on the Data line, one bit per Clock pulse, similar to what the attached device would do to transmit in the other direction.
The two clocks TXCLK and RXCLK are replaced by a single clock. This clock is an input to the PHY rather than an output, which allows the clock signal to be shared among all PHYs in a multiport device, such as a switch. The clock frequency is doubled from 25 MHz to 50 MHz, while the data paths are narrowed from 4 bits to 2 bits.
One drawback of using source-synchronous clocking is the creation of a separate clock-domain at the receiving device, namely the clock-domain of the strobe generated by the transmitting device. This strobe clock-domain is often not synchronous to the core clock domain of the receiving device. For proper operation of the received data with other ...