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IMPLEMENTATION OF IMPLEMENTATION OF µ - PROCESSORµ - PROCESSOR
DATA PATHDATA PATH
Project By:Project By:Daniel BrauchDaniel BrauchElad ShabtaiElad Shabtai
Barak SchlosserBarak Schlosser
Project Goals
• Designing and implementing the schematic and layout design of an 8 bit µProcessor data path , which will include an ALU Manchester carry look ahead and a barrel shifter.
• Testing the design for accuracy and performance.
Data Path overall design
Applications:
• The data path is the core element of every micro processor and thus included in every application that performs arithmetic calculations ,logic evaluation and data movement.
Implementation Notes :
• The ALU will be built from a Manchester carry look ahead adder and eight 1 bit ALU.
• The output of the ALU will be inserted into the shift register for shifting operations.
• The barrel shifter can perform up to 3 bit shifts in a single combinational function.
• The inputs for the ALU are valid on the rise of the clock.
Design Specifications:
• ALU:
• Inputs: two 8-bit words (A,B)3-bit ALU controls.
3-bit shift controls.
1-bit clock.
* Cin bit will be generated from the ALU control bits
• Output: 8-bit word (F), 1 carry out.
• Functions:A or B, A and B, A xor B, A + B,
A – B , B – A , Pass A, Pass B
Design Specifications:
• Barrel Shifter: • Can multiply by 1, 2 , 4 or 8 by shifting left 0, 1 ,2 or 3 bits.
• General:• Power supply: Vdd is set to 5 volts referenced to
ground.
• Size specifications: Final physical size must be optimized.
• Time specifications: All data and control bits are set on the rise of the clock. The maximum propagation delay for all functions must be less than 100ns.
Manchester Carry
Manchester Carry Chain
Manchester Carry explanation
• For each bit 2 values are calculated:• Pi = Ai XOR Bi• Gi = Ai AND Bi• On the rise of the clock the upper PMOS gates
are closed and the bottom NMOS are open enabling the pull down of the carry out bar.
• The Pi controls enables the propagation of the Cout signals.
• The max propagation delay is caused by the pulling down of all the carry out bar signals.
Manchester Carry cont.
• The main advantage of the Manchester chain is its small physical size.
• In terms of propagation delay the Manchester chain is situated in the middle of the scale.
Comparison between different Full Adders
0 10 20N
0.0
20.0
40.0
60.0
80.0
t p (
nse
c)
0 10 20N
0.0
0.2
0.4
Area
(m
m2
)look-ahead
select
bypass
manchester
mirrorstatic
manchester
look-ahead
select
static
mirrorbypass
1 bit ALU implementation
FULL
ADDER
XOR
MUX 4:1
MUX 4:1
LOGIC
AND
OR
B
A’
B
A
A’
0
0
B’
S2 S1
S1 S0
Cin
Out
ALU control bitsS2 S1 S0 OPERATION
0 0 0 B - A
0 0 1 OR
0 1 0 AND
0 1 1 A + B
1 0 0 XOR
1 0 1 PASS B
1 1 0 PASS A
1 1 1 A - B
000 : B - A
111 : A - B
001 : OR
010 : AND
100 : XOR
011 : A + B110 : PASS A101 : PASS B
CHAIN
F.A
XOR - 111
Equivalence
MUX 4:1 implementation
A
B
C
D
1 bit FULL ADDER implementation
C B A
SUM = A xor B xor C
** no need to compute carry out – calculated by Manchester carry look ahead
Tanner S-Edit
modules implementation
Manchester – module :
Simulation results :
0 5 10 15 20 25 30 35 40 45 50
Time (ns)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Vo
lta
ge
(V
)
v(Out3)5.00
v(Out4)5.00
v(Out5)5.00
v(Out6)4.99
v(Out7)4.99
x1= x2= dx=-912.46p 14.14n 15.06ntest_manchester_carry
Carry all:
Carry last – worst case propagation ~10ns:
0 5 10 15 20 25 30 35 40 45 50
Time (ns)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Vo
lta
ge
(V
)
v(Out3)
v(Out4)
v(Out5)
v(Out6)
v(Out7)
test_manchester_carry
Barrel shifter – module :
Simulation results - shifting 01001011:
0 5 0 1 0 0 1 5 0 2 0 0
Tim e ( ns )
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
3 .5
4 .0
4 .5
5 .0
Vo
ltag
e (
V)
v (Q 0 )
Unti tl ed
0 5 0 1 0 0 1 5 0 2 0 0
Tim e ( ns )
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
3 .5
4 .0
4 .5
5 .0
Vo
ltag
e (
V)
v (Q 1 )
Unti tl ed
0 5 0 1 0 0 1 5 0 2 0 0
Tim e ( ns )
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
3 .5
4 .0
4 .5
5 .0
Vo
ltag
e (
V)
v (Q 2 )
Unti tl ed
0 5 0 1 0 0 1 5 0 2 0 0
Tim e ( ns )
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
3 .5
4 .0
4 .5
5 .0
Vo
ltag
e (
V)
v (Q 3 )
Unti tl ed
0 5 0 1 0 0 1 5 0 2 0 0
Tim e ( ns )
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
3 .5
4 .0
4 .5
5 .0
Vo
ltag
e (
V)
v (Q 4 )
Unti tl ed
0 5 0 1 0 0 1 5 0 2 0 0
Tim e ( ns )
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
3 .5
4 .0
4 .5
5 .0
Vo
ltag
e (
V)
v (Q 5 )
Unti tl ed
0 5 0 1 0 0 1 5 0 2 0 0
Tim e ( ns )
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
3 .5
4 .0
4 .5
5 .0
Vo
ltag
e (
V)
v (Q 6 )
Unti tl ed
0 5 0 1 0 0 1 5 0 2 0 0
Tim e ( ns )
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
3 .5
4 .0
4 .5
5 .0
Vo
ltag
e (
V)
v (Q 7 )
Unti tl ed
1 bit ALU :
Data Path – modules :Define Cin :
Shifter :
Calculate Cin :
Alu1bit * 8 - 8 bit output :
Choose output from Alu / Manchester :
8 bit ALU - module :
Including :- Cin logic- Manchester chain- Alu- Cout logic
8 bit ALU - design :
8 bit ALU simulation - pass A (00000001) :
8 bit ALU simulation - AND A (10001001) B (10000001) :
DataPath –module :
DataPath simulation : (A + B) * 4
A=00001010 B=00000011
DataPath simulation : (A + B) * 4 A=00001010 B=00000011
VHDL
Simulation
VHDL – simulation resaults :
End – opCode 111 :
Start – opCode 000 :
Advantages of design :
• Parallel implementation of calculations.• Minimal number of transistors in current
implementation ~ 600 transistors
- Trivial implementation using mux 8*1 with scmos
implementation ~ 1300 transistors
- Less transistors thus low on power consumption
and faster in propagation ~ 40 ns
Milestones• Studying design options for the ALU, Manchester carry
look ahead and shifter - Due 01/06/04• Implementing all 3 units in gate level and testing them for
correctness and performance - Due 08/06/04• Combining units and testing overall design - Due 15/06/04• Creating VHDL test bench and comparing designs
- Due 22/06/04 • Grade : ?
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