Digital Logic Toolkit

Digital Logic Toolkit — Flip-flops & latches

Source
https://digitallogictoolkit.com/flip-flops/
Printed

D flip-flop, rising edge with D = 1 — flip-flops

corethe workhorse element

Answer

Q⁺ = 1

Why this example is worth doing

The characteristic equation is simply Q⁺ = D, which makes the D flip-flop the easiest element to reason about and the reason essentially all synchronous logic is built from it. The page shows the setup and hold window around the edge, because the equation is only true if the input is stable across that window, and a timing violation is not a logic error the truth table can show.

Try your own input in the Flip-flops & latches. SR, D, JK and T: characteristic tables, excitation tables and timing diagrams.

How the answer is reached

The probed row

D = 1, Q = 0

Output table

Output table — columns D, Q, Q⁺
DQQ⁺
000
010
101
111

Compare with

Open the Flip-flops & latches

This input is entered in the tool itself — it is too rich for a link to carry.

Note:

Notation this page assumes

  • Symbols: · is AND, + is OR, ⊕ is XOR, a prime or an overline is NOT. The field also takes ∧ ∨ ¬ ~ ! & | and the words.
  • Operator precedence, tightest first: NOT, then AND (including juxtaposition), then XOR/XNOR, then NAND/NOR, then OR, then IMPLIES, then IFF.
  • Gate symbols follow whichever standard the header toggle is set to: ANSI/IEEE Std 91-1984 distinctive shapes, or IEC 60617-12 rectangles.

Sources

  • ANSI/IEEE Std 91-1984, Graphic Symbols for Logic Functions
  • IEC 60617-12, Graphical Symbols for Diagrams — Binary Logic Elements