Combinational Circuit

1
Combinational Circuit MSI Circuit

• ENCODER
• With the aid of K-map (dont care situation), we
  can get
• D0 F1 F2
• D1 F2 F3

2
Combinational Circuit MSI Circuit

• ENCODER (Octal to Binary)
• At one time, only one input line has a value of 1
• Most of the time needs priority encoder

3
Combinational Circuit MSI Circuit

• ENCODER (Octal to Binary)
• Can you get 2n to n encoder without using
  Karnaugh map

4
Combinational Circuit MSI Circuit

• DEMULTIPLEXER
• Given input line sets of selection line,
  demultiplexer will send data directly from input
  to selected output line
• Example 1 to 4 Demultiplexer

5
Combinational Circuit MSI Circuit

• DEMULTIPLEXER
• Demultiplexer is similar to decoder with enable
  as follows

6
Combinational Circuit MSI Circuit

• MULTIPLEXER
• 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

7
Combinational Circuit MSI Circuit

• MULTIPLEXER
• Truth table for 4-1 multiplexer

8
Combinational Circuit MSI Circuit

• MULTIPLEXER
• 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 2n1 MUX is made from
  n2n decoder with 2n input line added, for each
  AND gate.

9
Combinational Circuit MSI Circuit

• MULTIPLEXER

10
Combinational Circuit MSI Circuit

• MULTIPLEXER
• Usage

11
Combinational Circuit MSI Circuit

• LARGE MULTIPLEXER
• Large multiplexer can be built from smaller
  multiplexer
• 81 multiplexer can be built from smaller
  multiplexer like this

12
Combinational Circuit MSI Circuit

• LARGE MULTIPLEXER
• Other example the building of 81 multiplexer
  from smaller multiplexer

13
Combinational Circuit MSI Circuit

• LARGE MULTIPLEXER
• 161 multiplexer can be
• built using five 41
• multiplexer

14
Combinational Circuit MSI Circuit

• MULTIPLEXER (Function Execution)
• Boolean Function can be executed using
  multiplexer
• 2n1 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

15
Combinational Circuit MSI Circuit

• MULTIPLEXER (Function Execution)
• This method succeed because
• Put 1 at I1,I2, I3, and 0 at the remaining

16
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)

17
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 dont care and
  variable input numbers is limited (e.g. 10 input
  1K, 16 input 64K, 20 input 1M)

18
Combinational Circuit (Programmable Logic Device)

• Read-Only-Memory (ROM)
• Ready-made ROM Device Type
• ROM Read Only Memory
• Data 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 ROM
• Semi-custom chip. Fuse can be burnt with
  special hardware programming unit. High cost
  for small quantity and it cannot be erased after
  programmed.

19
Combinational Circuit (Programmable Logic Device)

• Read-Only-Memory (ROM)
• Ready-made ROM Device Type
• EPROM Erasable PROM
• Similar with PROM only that data can be erased
  by exposing it to ultra violet light
• EEPROM Electrically EPROM
• PROM 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

20
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 n2n 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)

21
Programmable Read-Only-Memory (PROM)
22
Programmable Read-Only-Memory (PROM)
23
Programmable Read-Only-Memory (PROM)
24
Combinational Circuit (Programmable Logic Device)

• Execute logical function with PROM
• Example (8X3 ROM)
• First, convert each function to SOP

25
Execute logical function with PROM
26
Execute logical function with PROM