CENT-113 Digital Electronics 1 Flip Flops TI Type 502 Flip Flop: 1st production IC in 1960.

CENT-113 Digital Electronics 2 Interest 1919: W. H. Eccles and F. W. Jordan publish the first flip-flop circuit design. M74HC74AM Fairchild CMOS flip-flop for frequency manipulation is used in a Smart Card Reader.

CENT-113 Digital Electronics 3 Logic Circuit Classifications Combination Logic Circuits –Building block is the logic gate. –Use AND, OR, NOT gates. Sequential Logic Circuits –Building block is the flip flop (FF). –Used in timing and memory devices. –Flip Flops are wired to form counters, shift registers, and various memory devices.

CENT-113 Digital Electronics 4 R-S Flip Flop Logic Symbol Wiring Diagram Set Reset Complementary Normal S R Q Q FF Truth Table Waveform Diagram Mode of Operation Input S Input R Output Q Output Q Effect Prohibited 0011 Do not use Set 0110 For setting Q to 1 Reset 1001 Resetting Q to 0 Hold 11QQ Depends Previous State Input Output Input Output Set Reset Set Hold S R Q Q Also called: R-S Latch Set-Reset FF

CENT-113 Digital Electronics 5 Clocked R-S Flip Flop Logic Symbol Wiring Diagram Truth Table Waveform Diagram Mode of Operati on Input CLK Input S Input R Output Q Output Q Effect Hold 0011 No Change Reset 0101 Reset or cleared to 0 Set 1010 Set to 1 Prohibited 1111 Do not use Input Output S R Q Q Set Reset Complementary Normal InputOutput Clock S R Q Q FF CLK Output FF operates Synchronously in step with clock.

CENT-113 Digital Electronics 6 Questions Q. What type of waveform is used in flip flops? A. Square Waves. Q. What does the RS stand for in the RS Flip Flop? A. Reset Set.

CENT-113 Digital Electronics 7 D Flip Flop Logic Symbol Wiring Diagram Data Clock Complementary Normal D CLK Q Q FF Truth Table Similar Wiring Input Output Also called: Delay FF Data FF D-type Latches ‘Delayed 1 Clock Pulse’ Input CLK Input D Output Q n+1 Output Q D CLK Q Q FF S R Q Q CLK =

CENT-113 Digital Electronics D Flip Flop Logic Symbol Truth Table Data ClockComplementary Normal D CLK Q Q FF Input Output Mode of Operation INPUTSOUTPUTS AsynchronousSynchronous PSCLRCLKDQQ Asynchronous Set01XX10 Asynchronous Reset10XX01 Prohibited00XX11 Set11L to H110 Reset11L to H001 Note: The asynchronous inputs (PS & CLR) Override the synchronous inputs (D & CLK). PS Preset Clear CLR

CENT-113 Digital Electronics 9 D (Delay) Flip Flop Uses Sequential logic devices used in temporary memory devices. Wired together to form shift registers and storage registers. Delays data from reaching output Q one clock pulse. CMOS examples: 74HC74, 74FCT374, Over 50 different ICs in FACT CMOS family.

CENT-113 Digital Electronics 10 J-K Flip Flop Logic Symbol Truth Table Mode of Operation INPUTSOUTPUTSEffect Input CLK Input J Input K Output Q Output Q Hold 00 No Change No Change No Change Reset 0101 Reset or cleared to 0 Set 1010 Set to 1 Toggle 11 Changed to Opposite State Data Complementary Normal InputOutput Clock J K Q Q FF CLK Data

CENT-113 Digital Electronics J-K Flip Flop Logic Symbol Truth Table Mode of Operation INPUTSOUTPUTS AsynchronousSynchronous PSCLRCLKJKQQ Asynchronous Set01XXX10 Asynchronous Reset10XXX01 Prohibited00XXX11 Hold1100No Change Reset Set Toggle1111Opposite State Note: 7476 uses the entire pulse to transfer data from J & K data inputs to Q & Q outputs. Data Complementary Normal InputOutput Clock J K Q Q FF CLK Data Preset Clear CLR

CENT-113 Digital Electronics 12 J-K Flip Flop Uses Universal Flip Flop. Has all features of other FF. When being used only in the toggle mode, commonly called a T Flip Flop. CMOS examples: 74HC76, 74AC109, Most commonly used as counters.

CENT-113 Digital Electronics 13 Questions Q. What circuit can be used to give a clock signal? A. Astable multivibrater.

CENT-113 Digital Electronics 14 IC Latches Input Keyboard Encoder4-Bit LatchDecoder Output Display Decimal Binary A device that serves as a temporary buffer memory is called a latch. An example of a 4-bit latch is the A latch is transparent when the enable input is high, the normal outputs follow the data in the D inputs. One example of flip flops is to latch or hold data.

CENT-113 Digital Electronics 15 IC Latch Uses The latch is the fundamental memory device used in digital electronics. Almost all digital equipment contains simple memory devices called latches. CMOS examples: 4042, 4099, 74HC is an example of a BCD-7 Segment latch/decoder/driver chip.

CENT-113 Digital Electronics 16 CMOS D Flip-Flop Schematic

CENT-113 Digital Electronics 17 D Flip Flop using Nor gates What logic gates are more efficient?

CENT-113 Digital Electronics 18 CMOS D Flip-Flop CMOS technology allows a very different approach to flip-flop design and construction. Instead of using logic gates to connect the clock signal to the master and slave sections of the flip- flop, a CMOS flip-flop uses transmission gates to control the data connections.

CENT-113 Digital Electronics 19 Triggering Flip Flops The added inverter bubble at the clock input shows that triggering occurs on the negative going edge of the clock pulse. The J-K master/slave flip flop uses the entire pulse (positive edge and the negative edge) to trigger the flip flop. Waveform 165.

CENT-113 Digital Electronics 20 Schmidt Trigger Schmidt Trigger Inverter commonly used to square up input signal. This reshaping of the waveform is called signal conditioning.

CENT-113 Digital Electronics 21 IEEE vs. Logical Symbols See internet links.

CENT-113 Digital Electronics 22 Conclusions Q. What are some circuit uses for flip flops? A. Counters, shift registers, and various memory devices.