Combinational Circuit – MSI CircuitENCODER• With the aid of K-map (don’t care situation), we can get

D0 = F1 +F2D1 = F2 +F3

Combinational Circuit – MSI CircuitENCODER (Octal to Binary)• At one time, only one input line has a value of 1• Most of the time needs priority encoder

Combinational Circuit – MSI CircuitENCODER (Octal to Binary)

• Can you get 2n to n encoder without using Karnaugh map

Combinational Circuit – MSI CircuitDEMULTIPLEXER• Given input line & sets of selection line, demultiplexer

will send data directly from input to selected output line• Example: 1 to 4 Demultiplexer

Combinational Circuit – MSI CircuitDEMULTIPLEXER• Demultiplexer is similar to decoder with enable as

follows:

Combinational Circuit – MSI CircuitMULTIPLEXER• multiplexer is a device which consist of

– Several input line– Several select line– One output line

• It transmit one from 2n input line to one output line using n select line. It is also known as data selector

Combinational Circuit – MSI CircuitMULTIPLEXER• Truth table for 4-1 multiplexer

Combinational Circuit – MSI CircuitMULTIPLEXER• Output for multiplexer is Sum of the (product of

data lines and selection lines)• Example: Output for 4-1 multiplexer is

• 2n-to-1 line multiplexer or 2n:1 MUX is made from n:2n decoder with 2n input line added, for each AND gate.

Combinational Circuit – MSI CircuitMULTIPLEXER

Combinational Circuit – MSI CircuitMULTIPLEXER• Usage:

Combinational Circuit – MSI CircuitLARGE MULTIPLEXER• Large multiplexer can be built from smaller

multiplexer • 8:1 multiplexer can be built from smaller

multiplexer like this

Combinational Circuit – MSI CircuitLARGE MULTIPLEXER• Other example the building of 8:1 multiplexer

from smaller multiplexer

Combinational Circuit – MSI CircuitLARGE MULTIPLEXER• 16:1 multiplexer can be

built using five 4:1 multiplexer

Combinational Circuit – MSI CircuitMULTIPLEXER (Function Execution)• Boolean Function can be executed using multiplexer• 2n:1 multiplexer can execute Boolean function with n input

variable as the following– Expression in SOM

Example:

– Combine n variable to n selection line– Put 1 at data line if it is a minterm for that function, else 0

Combinational Circuit – MSI CircuitMULTIPLEXER (Function Execution)• This method succeed because

• Put 1 at I1,I2, I3, and 0 at the remaining

Combinational Circuit (Programmable Logic Device)

Read-Only-Memory (ROM)• Semiconductor memory is a device where data can be

stored and fetched• Logically, this memory device can be said as memory

cells table (data)

Combinational Circuit (Programmable Logic Device)

Read-Only-Memory (ROM)• ROM is a memory device where data can only be read but

cannot be written• Writing is done by special programming device

(programmable ROM)• Any Boolean function can be executed by using ROM. The

steps: Get TT, take its input as address and output as data• Advantage: Boolean function is executed directly• Disadvantage: Didn't use the “don’t care” and variable input

numbers is limited (e.g. 10 input – 1K, 16 input – 64K, 20 input – 1M)

Combinational Circuit (Programmable Logic Device)

Read-Only-Memory (ROM)• Ready-made ROM Device Type

– ROM: Read Only MemoryData is written to memory by “mask programming” when manufacturing process. High cost to start and very cost effective if produced in large quantity

– PROM: Programmable ROMSemi-custom chip. Fuse can be burnt with “special hardware programming unit”. High cost for small quantity and it cannot be erased after programmed.

Combinational Circuit (Programmable Logic Device)

Read-Only-Memory (ROM)• Ready-made ROM Device Type

– EPROM: Erasable PROMSimilar with PROM only that data can be erased by exposing it to ultra violet light

– EEPROM: Electrically EPROMPROM where data to be erased can be selected by “hardware programmer unit” other than ultra violet light. Very useful for isolated device where it can be reprogrammed from far

Combinational Circuit (Programmable Logic Device)

Programmable Read-Only-Memory (PROM)• Device with hardwired AND array (i.e. decoder) and

programmable OR array• AND array (decoder) execute 2n minterm product

combination for n input (known as n:2n decoder)• n line input and m line output• Input bit variable combination – address• Input bit combination for output line – word (each word

contain m bit)

Programmable Read-Only-Memory (PROM)

Programmable Read-Only-Memory (PROM)

Programmable Read-Only-Memory (PROM)

Combinational Circuit (Programmable Logic Device)

Execute logical function with PROM• Example (8X3 ROM) –

• First, convert each function to SOP

Execute logical function with PROM

Execute logical function with PROM