CHAPTER 6 Sequential Circuit Design By Pn Siti

CHAPTER 6 Sequential Circuit Design By : Pn Siti Nor Diana Ismail

Sequential Circuit Design ü ü ü Design procedure Finding state diagrams Finding state tables State assignment Designing with D flip-flops

Look example in Tutorial 4

Design procedure 1. 2. 3. 4. 5. 6. 7. Specification Formulation State assignment FF input equation determination Output equation determination Technology mapping Verification These are the proper procedure to design a complete sequential circuit.

Design procedure 1. Specification Usually this is given in form of statements. User need to extract important points. 2. Formulation 3. State assignment 4. Obtain state diagram and state table Assign binary codes to the states FF input equation determination Determine FF type Derive FF input equation from state table

Design procedure 5. Output equation determination 6. Derive output equation from state table Technology mapping Usually this is omitted Only use FF and basic gates in schematic 7. Verification

Finding state diagrams/state table When the diagram is given You need to find the state table On the other hand, when the state table is given You need to find the state diagram

Finding state diagrams/state table When the diagram is given You need to find the state table Try to find the state table for this

Finding state diagrams/state table When the diagram is given You need to find the state table

Finding state diagrams/state table On the other hand, when the state table is given You need to find the state diagram You can try on the same state table and diagram or on this one

State assignment For a 2 bit state (let’s say Q 1 Q 0) you will have at most 4 states 00 01 10 11 You may assign the states with variables Eg : A = 00, B = 01, C = 10, D = 11

Designing with D flip-flops A state table is given (you may want to convert it to a 1 -D table)

Designing with D flip-flops Present State Input Next State Output DA = A DB = B Z A B X 0 0 1 1 0 1 0 1 0 0 0 1 1 0 1 0 1 0 0

Designing with D flip-flops You will get the input equation from state table Use K-map to get the equation for DA DB Z

Designing with D flip-flops You will get these equations Now you can draw the schematic diagram using D FF

Exercise A sequential circuit has two FF, A and B, one input, X, and one output, Y. The state diagram is shown below. Design the circuit with D flip-flops.

Introduction to Memory Collection of cells capable of storing binary information Contains electronic circuits for storing & retrieve information Used to provide temporary or permanent storage capability

Memory Basic Process n n n Info/content from memory is send to h/w (usually consist of registers & combinational logic) to be processed The processed info is then returned to the same or different memory address Input and Output devices may also interact with memory Printers Mouse Keyboard Monitor Digital Camera Scanners Plotters Thumb Drive External Memory I/O Memory Hardware for processing

Types of Memories Random Access Memory (RAM) Write operation – stores new info Read operation – transfer the stored info out of memory Read Only Memory (ROM) Perform read operation only

Memory data elements Typical data elements are: bit : a single binary digit byte : a collection of eight (8) bits accessed together word : a collection of binary bits whose size is a typical unit of access for the memory. (e. g. , 1 byte, 2 bytes, 4 bytes, 8 bytes, etc. ) Memory Data ─ a bit or a collection of bits to be stored into or accessed from memory cells. Memory Operations ─ operations on memory data supported by the memory unit. Typically, read and write operations over some data element (bit, byte, word, etc. ).

Memory Organization Example: • address bits = m = 10 • data bits =16; n = 16 • Address line = (2 m) 210 = 1024 or 1 K, labeled 0 to 1023 • memory content = 16 -bit • so the memory has 1 K words of 16 bit data or 1 K x 16 -bit memory Note : K (Kilo) = 210 M (Mega) = 220 G (Giga) = 230 Other Example : 64 K = 216 = (26 * 210) 2 M = 221 = (21 * 220) 4 G = 232 = (22 * 230) What is the address bits (m)?