Midterm%20Wednesday

1
Midterm Wednesday

• Chapter 1-3
• Number /character representation and conversion
• Number arithmetic
• Combinational logic elements and design
  (DeMorgans Law)
• Sequential logic elements and design (State
  machines)
• Memory organization and implementation
• Clocks and timing

2
Overview
The von Neumann Machine - The programmable
digital computer (both program and data are
stored in the computer memory) - Computer
comprised of processing unit, memory, control
unit, input(s), and output(s) Introducin
g the LC-3 Computer - A toy computer for us
to learn from 16 bit machine, word
addressable, 64K or 65,536 locations
(Could it have an address space of 1 Gig? 1 Gig
needs 30 bits of addressing) Computer Machine
Instructions Computer native instructions
- The basic instructions that all programs use on
that computer (The atomic unit of work
done by a computer) The Instruction Cycle
- The steps in the execution of a machine
language instruction (Fetch, Decode,
Evaluate Address(es), Fetch operand(s), Execute,
and store results)
3
The LC-3 Computera von Neumann machine
4
From Logic to Data Path

• Data Paths
• The data path of a computer is all the logic
  used to process
• information.
• See the data path of the LC-3 on next slide.
• Combinational Logic
• Decoders -- convert instructions into control
  signals
• Multiplexers -- select inputs and outputs
• ALU (Arithmetic and Logic Unit) -- operations on
  data
• Sequential Logic
• State machine -- coordinate control signals and
  data movement
• Temporary (scratchpad) Memory
• Registers and latches -- storage elements

5
LC-3 Data Path
Combinational Logic
Storage
State Machine
6
Data Path of the LC-3
7
Computer Machine Instruction Formats

• What is IN an instruction?
• Specifies the operation to be performed
• Where to get the operands
• Where to put the result
• What are the major instruction types?
• Data Movement (load, store, etc.)
• Operate (add, sub, mult,OR, AND, etc.)
• Control (branch, jump to subroutine, etc.)

8
The Machine Instruction

• Necessary information
• Operation code
• Input Operand(s)
• Output Operand(s)
• Typical Operation formats
• 1 operand
• 2 operands
• 3 operands
• Alternative Instruction Design Strategies
• Cisc (Complex Instruction Set Architecture)
• Risc (Reduced Instruction Set Architecture)

9
The LC-3 Instruction

• FORMAT generally 2 operand
• Operation code
• Input Operand(s)
• Output Operand(s)
• Where are the operands?
• Memory
• Registers