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 Number System Conversions Between Number System Arithematic Operations 1's & 2's Complement Gray Codes Arithmetic Circuits Logical Gates and Truth Table Funtions Boolean Expressions Boolean Algebra Karnaugh Map Multiplexer DeMultiplexer Encoder & Decoder TTL Circuits Multivibrators 555 Timer Flip Flops RS Flip - Flop JK Flip - Flop D Flip - Flop Shift Register Schmitt Trigger Asynchronous Counters Synchronous Counters Digital - Analog Conversion Data Flow ROM Memory Drives Electronics Equation Resistor Color Codes

## Flip-Flops

"Flip-flop" is the common name given to two-state devices which offer basic memory for sequential logic operations. Flip-flops are heavily used for digital data storage and transfer and are commonly used in banks called "registers" for the storage of binary numerical data.

### Edge Triggering

Edge triggering is when the flip-flop state is changed as the rising or falling edge of a clock signal passes through a threshold voltage. This true dynamic clock input is insensitive to the slope or time spent in the high or low state.

Figure: A slow or delayed gate can be used to convert a level change into a short pulse. Both types of dynamic triggering are represented on a schematic diagram by a special symbol near the clock input. In addition to the clock and data inputs most IC flip-flop packages will also include set and reset (or mark and erase) inputs. The additional inputs allow the flip-flop to be preset to an initial state without using the clocked logic inputs.

Figure: The schematic symbols for
a) a positive edge-triggered JKFF,
b) a negative (falling) edge-triggered JKFF and
c) a negative edge-triggered JKFF with set and reset inputs.