D latch, transparent when enabled — flip-flops

corelevel-sensitive, not edge-triggered

Answer

Q⁺ column 01010011

Why this example is worth doing

A D latch follows its input continuously for as long as the enable is high, which is called transparency and is the property that distinguishes a latch from a flip-flop. The page draws the timing diagram showing the output tracking the input mid-pulse, and states plainly that this is why latches are difficult in synchronous design: the window during which data can change the state has a width rather than being an instant.

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

Output table

Output table — columns EN, D, Q, Q⁺
ENDQQ⁺
0000
0011
0100
0111
1000
1010
1101
1111

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