数字电路英文版-第八单元.pptVIP

KEY TERMS Astable Having no stable state. An astable multivibrator oscillates between two quasistable states. Asynchronous Having no fixed time relationship. Bistable Having two stable states. Flip-flops and latches are bistable multivibrators. Clear An asynchronous input used to reset a flip-flop ( make the Q output 0 ). D flip-flop A type of bistable multivibrator in which the output assumes the state of the D input on the triggering edge of a clock pulse. Edge-triggered flip-flop A type of flip-flop in which the data are entered and appear on the output on the same clock edge. Feedback The output voltage or a portion of it that is connected back to the input of a circuit. Hold time The time interval required for the control levels to remain on the inputs to a flip-flop after the triggering edge of the clock in order to reliably activate the device. Latch A bistable digital circuit used for storing a bit. Hystersis A characteristic of a threshold-triggered circuit, such as the Schmitt trigger, where the device turns on and off at different input levels. J-K flip-flop A type of flip-flop that can operate in the SET, RESET, no-change, and toggle modes. Master-slave flip-flop A type of flip-flop in which the input data are entered into the device on the leading edges of clock pulses and apper at the output on trailing edges. Master-slave flip-flops have, for the most part, been replaced by edge-triggered types. Monostable Having only one stable state. A monostable multivibrator, commonly called a one-shot, produces a single pulse in response to a triggering input. One-shot A monostable multivibrator. Preset An asynchronous input used to set a flip-flop ( make the Q output 1 ). RESET The state of a flip-flop or latch when the output is 0; the action of producing a RESET state. SET The state of a flip-flop or latch when the output is 1; the action of producing a SET state. Set-up time The time interval required for the control