Integrated Circuits

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Integrated Circuits
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Integrated Circuit (IC)

• A silicon crystal (chip) containing electronic
  components that create the logic gates weve been
  looking at
• SSI Small Scale Integration
• MSI Medium Scale Integration
• LSI Large Scale Integration
• VLSI Very Large Scale Integration
• These refer to the number of logic gates
  contained on the chip

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Technologies

• TTL Transistor-Transistor Logic
• ECL Emitter-Coupled Logic
• MOS Metal-Oxide Semiconductor
• CMOS Complementary Metal-Oxide Semiconductor
• These refer to the underlying characteristics of
  the process for turning silicon into gates

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Digital Components

• Decoder
• Encoder
• Multiplexer
• Register
• Shift Register
• Counter
• Memory

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Decoder

• Convert n input bits to a single output bit
• For example converting binary to octal (3-to-8)
• What does the circuit look like?
• Start with a truth table

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Decoder Chaining

• Decoders can be chained
• Enable bit acts as the 4th input bit
• We now have a 4-to-16 decoder

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Encoder

• Inverse of a decoder
• Convert one input bit to multiple output bits
• For example converting octal to binary (8-to-3)

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Multiplexer

• Routes one of 2n input data lines to a single
  output line based on n selection lines
• How many inputs total?
• How big is the truth table?

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Multiplexer

• 6 total inputs (4 data lines, 2 selector lines)
  leads to 26 64 rows of truth table!
• This is excessive and tedious
• More conveniently shown thusly
• Built from an n-to-2n decoder with additional 2n
  input data lines

Select Select Output
S1 S0 Y
0 0 I0
0 1 I1
1 0 I2
1 1 I3
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Multiplexer
I0
I1
Output
I2
I3
Not derived directly from the abridged truth
table but from your knowledge of decoders
S0
S1
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Register

• A multi-bit storage element made up of a group of
  flip-flops
• Recall flip-flops store 1 bit each

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Register

• CLR is a clear input for asynchronous
  initialization
• Data can be read out at any time
• Data is input with the clock signal, referred to
  as loading
• Loading can be further controlled through the use
  of additional combinational circuitry

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Shift Register

• Like a normal register only bits can be shifted
  from one flip-flop to the next

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General Purpose Shift Register

• Bidirectional shifting (left and right)
• Serial input/output
• Parallel load
• Parallel output
• A multiplexer is provided to select the operation

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General Purpose Shift Register

• Multiplexer operation selection
• Use a multiplexer to determine the shift operation

Mode Control Mode Control
S1 S0 Operation
0 0 No Change
0 1 Shift Right
1 0 Shift Left
1 1 Parallel Load
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General Purpose Shift Register

• What are they good for?
• Integer multiplication by powers of 2
• Integer division by powers of 2
• Bit counting for parity
• etc.

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Counter

• A register that cycles though predetermined
  states based on an external input
• Weve seen these already
• You should already know how to design one of
  these
• Parallel load/clear functionality is often added
  via combinational circuitry

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Memory

• A group of storage cells and associated access
  circuits
• Bits are grouped into words
• Words are the smallest addressable unit
• Typically made up of 1 or more bytes (8-bits)
• Each word in memory is assigned a unique address

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Memory
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Memory

• How many address lines?
• How many data input lines?
• How many data output lines?

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Memory

• K Kilo-bytes 210 bytes
• M Mega-bytes 220 bytes
• G Giga-bytes 230 bytes
• May be specified in either bytes or words
• Micro-processors will often talk of Kilo-bits
  or Mega-bits
• Be careful

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Memory Read/Write

• Read
• Apply binary address on the address lines
• Apply a signal to the read input
• Data is available on the data output lines
• Write
• Apply binary address on the address lines
• Apply binary data to the data input lines
• Apply a signal to the write input

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Memory

• Two types
• RAM Random Accessible Memory
• Operations we just looked at
• ROM Read Only Memory
• Has no input data lines
• Has no write input
• Has no read input (doesnt need it just acts
  when a valid address is supplied)

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ROM

• Significantly cheaper than RAM since it lacks
  versatility
• How does the data get in there?
• Mask programming data is programmed in at the
  time of silicon fabrication
• PROM special programming devices allow the user
  to write data one time
• EPROM data is erased under ultra-violet light
  or electronically, but must be entirely erased
  and rewritten (cant write single words)

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To Do

• Read chapter 2, if you havent already
• Problems 2-1, 2-3, 2-6, 2-7, 2-8, 2-12, 2-13,
  2-14, 2-16, 2-19, 2-20
• Assembly language
• A sequence of ASCII characters are stored in
  memory (you choose where)
• The length of the sequence is stored in register
  R0
• See next page for picture

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Example initial set up
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To Do

• Assembly language (continued)
• Write an 8051 program to determine if the
  sequence is a palindrome
• The output will be
• R1 0 if the value is not a palindrome
• R1 1 if the value is a palindrome
• Test your code on various sequences (both even
  and odd lengths, palindromes and not palindromes)
• Read chapter 4