Coursework 2
Computer Processors (XJCO1212)
The files required to complete this coursework are available on Minerva.
You should complete the coursework in the files provided, do not rename
any of the files or change the directory structure.
Submission You must submit your work via Minerva.
1 Minerva: Ensure that the coursework directory is compressed into
a .tar.gz archive and submitted to the Minerva.
Late submissions are accepted up to 7 days late. Each day, or part of
a day, will incur a 5% penalty.
Deadline See Minerva submission.
Weighting This piece of summative coursework is worth 15% of your grade.
This coursework involves implementing components of a computer processor
covered in the lectures. You should provide an implementation of each
of the following components in hdl. You are provided with a description of
the behaviour of each of the components as well as test files to ensure it
behaves according to specification.
Implement the following .hdl files
- HalfAdder.hdl
- FullAdder.hdl
- Add16.hdl
- ALU.hdl
- Bit.hdl
- Register.hdl
- Inc16.hdl
- PC.hdl
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- RAM8.hdl
- RAM64.hdl
- RAM512.hdl
- RAM4K.hdl
- RAM16K.hdl
- CPU.hdl
- Computer.hdl
In addition you should provide a reflective account of your coursework covering
the following point.
- What have you learned?
- What did you struggle with and why?
- What will you need to revise before the exam?
The reflective account is submitted via a Minerva test.
Marking
The marking of the .hdl files is automated so it is important that you do not
rename or alter the directory structure of your submission from that provided
on Minerva. Marks will be allocated in the following way:
- 10 marks for correct implementation of the components according to
their specification
- 3 marks for minimising complexity of the implementations
- 2 marks for the reflective account.
Chip descriptions
Chip name: HalfAdder
Inputs: x, y
Outputs: sum, carry
Function: Computes the sum of two bits.
Chip name: FullAdder
Inputs: x, y, z
Outputs: sum, carry
Function: Computes the sum of three bits.
Chip name: Add16
Inputs: x[16], y[16]
Outputs: result
Function: Adds two 16-bit values. The most significant carry bit is ignored.
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Chip name: ALU
Inputs: x[16], y[16], zx, nx, zy, ny, f, no
Outputs: out[16],zr,ng
Function: Computes one of the following functions: x + y, x − y, y − x,
0, 1, −1, x, y, −x, −y, ¬x, ¬y, x + 1, y + 1, x − 1, y − 1, x ∧ y, x ∨ y
on two 16-bit inputs, according to 6 input bits denoted zx, nx, zy,ny,
f, no. The bit-combinations that yield each function are documented
Figure 2.6 of The elements of Computing Systems. In addition, the
ALU computes two 1-bit outputs: if the ALU output is 0, zr is set to
1; otherwise zr is set to 0; If out < 0, ng is set to 1; otherwise ng is set
to 0.
Chip name: Bit
Inputs: x, load
Outputs: out
Function: If load[t] = 1 then out[t + 1] = x[t] else out does not change
(out[t + 1] = out[t])
Chip name: Register
Inputs: x[16], load
Outputs: out[16]
Function: If load[t] = 1 then out[t + 1] = x[t] else out does not change
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Chip name: Inc16
Inputs: x[16]
Outputs: out[16]
Function: 16-bit incrementer: out = x + 1 (arithmetic addition)
Chip name: PC
Inputs: x[16], load, inc,reset
Outputs: out[16]
Function: A 16-bit counter with load and reset control bits.
if (reset[t] == 1) out[t + 1] = 0
else if (load[t] == 1) out[t + 1] = in[t]
else if (inc[t] == 1) out[t + 1] = out[t] + 1 (integer addition)
else out[t + 1] = out[t]
Chip name: RAM8
Inputs: x[16], load, address[3]
Outputs: out[16]
Function: Memory of 8 registers, each 16 bit-wide. ‘Out’ holds the value
stored at the memory location specified by address. If load= 1, then
the ‘x’ value is loaded into the memory location specified by address
(the loaded value will be emitted to out after the next time step.)
Chip name: RAM64
Inputs: x[16], load, address[6]
Outputs: out[16]
Function: Memory of 64 registers, each 16 bit-wide. ‘Out’ holds the value
stored at the memory location specified by address. If load= 1, then
the ‘x’ value is loaded into the memory location specified by address
(the loaded value will be emitted to out after the next time step.)
Chip name: RAM512
Inputs: x[16], load, address[6]
Outputs: out[16]
Function: Memory of 512 registers, each 16 bit-wide. Out holds the value
stored at the memory location specified by address. If load=1, then
the in value is loaded into the memory location specified by address
(the loaded value will be emitted to out after the next time step.)
Chip name: RAM4K
Inputs: x[16], load, address[12]
Outputs: out[16]
Function: Memory of 4K registers, each 16 bit-wide. Out holds the value
stored at the memory location specified by address. If load=1, then
the in value is loaded into the memory location specified by address
(the loaded value will be emitted to out after the next time step.)
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Chip name: RAM16K
Inputs: x[16], load, address[14]
Outputs: out[16]
Function: Memory of 16K registers, each 16 bit-wide. Out holds the value
stored at the memory location specified by address. If load=1, then the
in value is loaded into the memory location specified by address (the
loaded value will be emitted to out after the next time step.)
Chip name: CPU
Inputs: inM[16], instruction[16],reset
Outputs: outM[16], writeM ,addressM[16], pc[15]
Function: Consists of an ALU and a set of registers, designed to fetch and
execute instructions written in the Hack machine language. In particular,
functions as follows: Executes the inputted instruction according
to the Hack machine language specification. The ‘D’ and ‘A’ in the language
specification refer to CPU-resident registers, while ‘M’ refers to
the external memory location addressed by ‘A’, i.e. to Memory[A]. The
‘inM’ input holds the value of this location. If the current instruction
needs to write a value to ‘M’, the value is placed in ‘outM’, the address
of the target location is placed in the ‘addressM’ output, and the
‘writeM’ control bit is asserted. (When ‘writeM’= 0, any value may appear
in ‘outM’). The ‘outM’ and ‘writeM’ outputs are combinational:
they are affected instantaneously by the execution of the current instruction.
The ‘addressM’ and ‘pc’ outputs are clocked: although they
are affected by the execution of the current instruction, they commit
to their new values only in the next time unit. If ‘reset’= 1 then the
CPU jumps to address 0 (i.e. sets ‘pc’= 0 in next time unit) rather
than to the address resulting from executing the current instruction.
Chip name: Computer
Inputs: reset
Outputs:
Function: The HACK computer, including CPU, ROM and RAM. When
reset is 0, the program stored in the computer’s ROM executes. When
reset is 1, the execution of the program restarts. Thus, to start a
program’s execution, reset must be pushed “up” (1) and “down” (0).
From this point onward the user is at the mercy of the software. In
particular, depending on the program’s code, the screen may show some
output and the user may be able to interact with the computer via the
keyboard.