Logisim 1.0 D/J-K Flip-Flop

Library: Legacy

Introduced: 2.0 Beta 12

Appearance:

Behavior

The reason for this component is for backwards compatibility with Logisim 1.0X; for new circuits, the Memory library's flip-flops are recommended instead.

Each flip-flop stores a single bit of data, which is emitted through the Q output on the east side. Normally, the value can be controlled via the inputs to the west side. In particular, the value changes when the clock input, marked by a triangle on each flip-flop, rises from 0 to 1; on this rising edge, the value changes according to the corresponding table below.

D Flip-Flop

J-K Flip-Flop

`D`	`Q`
0	0
1	1

`J`	`K`	`Q`
0	0	`Q`
0	1	0
1	0	1
1	1	`Q`'

Another way of describing the different behavior of the flip-flops is in English text.

D Flip-Flop: When the clock rises from 0 to 1, the value remembered by the flip-flop becomes the value of the D input (Data) at that instant.
J-K Flip-Flop: When the clock rises from 0 to 1, the value remembered by the flip-flop toggles if the J and K inputs are both 1, remains the same if they are both 0, and changes to the K input value if J and K are not equal. (The names J and K do not stand for anything.)

Pins

West edge, marked by triangle (input, bit width 1): Clock input: At the instant that this input value switches from 0 to 1 (the rising edge), the value will be updated according to the other inputs on the west edge. As long as this remains 0 or 1, the other inputs on the west edge have no effect.
West edge, other labeled input(s) (input(s), bit width 1): These inputs control how the flip-flop's value changes during the rising edge of the clock. Their exact behavior depends on the flip-flop; the above tables summarize their behavior.
East edge, labeled Q, north end (output, bit width 1): Outputs the value currently stored by the flip-flop.
East edge, south end (output, bit width 1): Outputs the complement of the value currently stored by the flip-flop.

Attributes

None.

Poke Tool Behavior

Clicking a flip-flop using the Poke Tool toggles the bit stored in the flip-flop, unless the asynchronous set/reset inputs currently pin the flip-flop's value.

Text Tool Behavior

None.

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