Introduction to Sequential Circuits

Notes

• This is chapter 6 of Carpanelli.
• In conbinational logic the outputted is completely determined by the input.
• In sequential logic
  • there is a state, or current status of the circuit
  • Input will change the stat
  This is exactly what we have seen with registers.
• Sequential logic = circuits with memory
• Frequently sequential logic involves some form of synchronization
• This is usually done in the form of a clock
  • A clock is a source of a periodic wave, or a periodic translation between 0 and 1.
  • A single cycle is the time it takes for one period
  • This is measured in time periods like microseconds, nanoseconds, picoseconds
  • The frequency of the clock is the number of cycles per second.
  • This is also known as Hertz, Hz (or cycles per second)
  • (From the book)
  • The image is an idealized clock output.
    • The actual output is not square and does not instantly change from 0 to 1 and 1 to 0.
  • The place where the clock changes from 0 to 1 is called the leading edge.
  • The place where the clock changes from 1 to 0 is called the trailing edge
  • Clocks have a duty cycle
    • This is the percent of a cycle where the value is high.
    • In the picture it is 50%, but it doesn't have to be.
  • Clocks are built at an electronic level outside of our scope of study.
  • But if you wish, Ben Eater builds a clock for his 8 bit computer here.
  • frequency = cycles/second
  • period = seconds/cycle