Arithmetic Logic Unit Design
for the
Simple RISC Computer
Group: E=MJ2
Arithmetic Logic Unit Design
•
•
•
•
•
•
•
•
Objective
Introduction
Design
Implementation
Components
Timing Diagrams
Conclusion
References
Objective
•
•
•
Learn and experience the benefits of
VHDL
Design the components of an ALU
that perform the predefined functions
specified for the SRC.
Implement them in VHDL to simulate
the operations of the ALU.
Introduction
•
ALU (“Arithmetic and Logic Unit”)
– Responsible for certain arithmetic and logic
functions. (Ex:addition,substaction,and, xor
etc).
•
The Control Unit (“CU”)
– Keep all elements of the ALU working in a
harmonic way.
•
Different Components can be added as
modules to help perform certain operations
– Adder, Shifter, Delatch, etc…
Design
Components
•
Adder
Arithmetic functions are
perform in this circuits.
1-bit adder
8-bit adder
Components
•
ASI
Receive the operand of
add, subtract and
increment
1-bit adder
8-bit ASI
8-bit ASI pkg
Components
•
Negator
Arithmetic functions are
perform in this circuits.
8-bit negator
8-bit negator pkg
Components
•
Register
Its is use for the ADC
function. The rest of the
functions done via the 2
buses.
8-bit register
8-bit register pkg
Components
•
Logic
This circuit performs the
logic functions and, or and
all of the shifting
operations.
1-bit logic/shifter
1-bit logic/shifter pkg
It is copied 8 times to work
as an 8 bit circuit.
Timing Diagram
Conclusion
•
•
•
In our design we were able to create an
ALU capable of completing all of the logic
and arithmetic functions specified in our
simulator.
The design can be used for further
continuation of a project, in which it can be
used as the ALU of a microcontroller or
CPU.
Our ALU might not have the fastest
performance, but it has one of the simplest
hardware designs.
References
•
•
Computer System Design Architecture, second ed,
Vincent P. Heuring and Harry F. Jordan.
A 32-Bit ALU Design Example,
http://lgjohn.ecen.ceat.okstate.edu/5253/lectures/
aludesver.pdf
Questions