Lecture 1 Notes

EENG3150 Digital Technologies - Lecture 1: Sequential Logic

• Combinational circuits: Outputs depend only on the current inputs at that specific time.

• Sequential circuits: Outputs depend on both the current inputs and the previous outputs (past history/state of the circuit).

Synchronous vs Asynchronous Sequential Circuits

• Asynchronous circuits:

  • Also known as unlocked circuits.They operate without a global clock signal, allowing changes in outputs to occur immediately in response to changes in inputs, which can lead to faster operation but also increases the complexity of timing analysis.

  • The output changes immediately based on the input, without any clocking signal.

  • note that All combinational circuits are asynchronous (no clock), but

  • Not all asynchronous circuits are combinational — because asynchronous sequential circuits include memory elements.

• Synchronous circuits:

  • Clocked circuits.

  • The output changes only at specific times dictated by a clock signal.

    

SR (Set/Reset) Latch

Key Differences

• Combinational vs. Sequential Circuits.

• Asynchronous vs. Synchronous Circuits.

• SR Latch implementations (NOR-gate and NAND-gate).