Deadline: Sunday 21st October
The overall aim of your assignment is to build a software based
implementation of a Central Processing Unit (CPU). Such an implementation
should be capable of simulating the execution of machine code
implementation should be written in the ‘C’, programming language but you
are free to use ‘C++’ if you are more comfortable with the latter. However,
in both cases you should use the GNU tool-chain to build the program. CPUs
can clearly be very complex devices, hence you will not be expected to
build a fully compliant implementation. However the more complete the
implementation, the higher the final grade will be. The CPU to be simulated
will be a loosely based on the standard ARM architecture. You will be
provided with a datasheet which will specify the nature of the device (e.g.
register count, status register format etc. and the instruction set to be
supported). In order for the simulation to work your program will also have
to provide some virtual peripheral devices. e.g. Some virtual RAM will be
The project has been broken down into four requirements described as
*Requirement 1 – Program Design (30% max) -(23/10/12).*
The first requirement will be to undertake some initial design work for the
product. This will require the development of a written design document,
which may also include block diagrams, that defines the overall
architecture of the system you intend to build. This should be a maximum of
*three pages *in length. The purpose of this work is to ensure you have a
clear understanding of the major tasks to be performed by your simulation
program. For example you may break down a solution along the following
Under each of these headings you could describe the major tasks to be
performed for that stage. You may also need to consider how the
current‘state’ of the CPU (and possibly the memory content) is to be shown.
e.g. following the execution of each instruction you may decide to show the
contents of the main registers and anything else that has been changed as a
result of the last instruction.
One key aspect you will have to consider is how the instructions will be
defined and read by your simulator. The op-codes should be stored in your
virtual RAM (or ROM if you decide to include such a feature). However these
codes need to get into the virtual machine somehow. Initially you may want
to consider hard-coding some simple instructions for testing purposes.
Later you may decide to load the instructions from a file.
*Requirement 2 – (30%-59%)*
The second requirement of the assignment is the implementation of the basic
CPU simulator. This should result in the development of a computer program
which has the ability to fetch, decode and execute several of the main
instructions within the provided instruction set. Including basic ALU type
instructions (e.g. ADD, SUB), Some Program Counter (PC) related
instructions (e.g. branching) and memory access instructions (LDR and STR).
*Requirement 3 – (60%-69%)*
The third requirement will be to extend requirement two so that it
simulates a full implementation of the provided instruction set. You should
take care to ensure that the instructions not only undertake their
operation correctly, but they also carry out appropriate side effects, such
as the setting of status register flags.
To get to the higher bracket of the available marks you should also include
the ability to count elapsed time during the simulation. To implement this
feature you will need to use the instruction timing information provided in
the datasheet and keep a running total of total time elapsed.
*Requirement 4 – (70%+)*