More Hardware Logic

1
More Hardware Logic

• More Hardware Logic
• NAND Gate
• NOR Gate
• Latch (Memory)
• Computer Architecture
• Processor Components
• Fetch-Execute Cycles
• Machine Language

2
NAND Gate

• NAND NOT AND
• Same as

0
1
0
1
1
1
1
0
3
NOR Gate

• NOR NOT OR
• Same as

0
1
0
1
0
1
0
0
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Latch (Memory)

• A latch can remember one binary digit
• A group of latches is called a register
• A register can store a binary value of a specific
  length in binary digits (bits)
• Standard register sizes are
• Eight bits ? One Byte
• Sixteen bits ? One Word
• Thirty two bits ? One Long Word

5
Logic for a Latch

• A latch circuit (Corrected from Figure 7.15)

D Value of Bit To be stored
Q Value of Bit Remembered
G Gate Signal To Store/Hold
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Try a latch with Logg-O

• Go to AE On-Line Web Site
• Go to Module 7
• Go to Lab 7.4
• Build and Test a Latch Circuit

7
Memory Cell

• Based on Latch (Modified Figure 7.17)

Data In / Out
Read 0 Write 1
D
Q
Latch
G
Select
Modified here to work with our Latch circuit
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Four Bit Register

• Based on Four Memory Cells (Fig 7.18)

D0
D1
D2
D3
Read 1 Write 0
One Bit Memory Cell
One Bit Memory Cell
One Bit Memory Cell
One Bit Memory Cell
Address Selected
9
Computer Architecture

• Processor Components

Data Bus
Instruction Register
Address
2
Mux
Decode
Program Counter
Arith Logic Unit
Accumulator
Memory Data and Instructions
10
Computer Architecture

• Instruction Fetch
• Program counter used as address to memory
• Instruction fetched from memory
• Instruction decoded
• Operation code (What to do)
• Address of data in memory to use (if applicable)
• Instruction Execute
• Data fetched from memory
• Arithmetic or logic performed
• Data stored in memory
• Program counter updated

11
Computer Architecture

• Machine Language Instructions
• Portion of instruction is operation code
• Portion of instruction may be immediate data
• Portion of instruction may be memory address
• Machine Language Instruction Format
• Single word / multi-word instruction formats
• Different bits in word(s) used for each field
• Hard to program in binary code words!!
• Leads to need for an assembly language

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Computer Architecture

• PIPPEN Machine / Assembly Language

Machine Language
Assembly Language
Direct Mode Operand
Direct Mode Operand
0000 CCCC AAAAAAAA
OPN A (A is an address)
Immediate Mode Operand
Immediate Mode Operand
0000 CCC0 NNNNNNNN
OPN N (N is a number)
No Operand
No Operand
OPN
0000 CCC0 --- unused ---
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Computer Architecture

• Look at Computer Simulation
• Go to AE On-Line Web Site
• Go to Module 7
• Go to Lab 7.5
• Starting with this in Module 6 next time