FINITE STATE MACHINE with DATAPATH

FSMD MODELData inputs Data outputs Controller outputs Status signals Control signals Controller inputs Datapath  performs the computations on data Controller  indicates to the datapath

FINITE STATE MACHINE with DATAPATH

SYNTHESIS

Dr Le Dung

Hanoi University of Science and Technology

FSMD MODEL

Data inputs

Data outputs Controller outputs

Status signals

Control signals

Controller

inputs

Datapath  performs the computations on data

Controller  indicates to the datapath which operations have to

be carried out on which data (algorithm)

Datapath Design

Temporary storage:

 registers, (shift registers), counters, register files, FIFOs, LIFOs

Functional units:

 arithmetic units, logical units and (barrel shifter)

Connections:

 data busses, multiplexers, tri-state buffers

Shift register (temporary store)  Register (temporary store)

Barrel shifter (functional unit)

Temporary storage

Register

R L Load

Reset

Inputs

Output

R

L Load Reset

Inputs

Output

U/D Up/Down C Clock

Register Files

2n

RE

WE

Read Enable

Inputs

Output

C Clock

Write Enable

RA(n)

WA(n)

Read Address

(n bits)

Write Address

(n bits)

Register Files

Functional Units

• Arithmetic units : Adder, Subtractor, Multiplier, Divider

• Logical units : Comparator, AND, OR, XOR …

• Barrel shifter : a digital circuit that can shift a data word

by a specified number of bits in one clock cycle

Eight-bit Barrel Shifter

8-bit Barrel shifter

Shift Number (0-7)

8 bits input

8 bits output Sh

Nr

Generic structure of the Datapath

Temporary storage

External inputs

External outputs

Result switching network

Functional units Operand switching network

Connections

Connections

Connections

Connections in Datapath

ROE

Outputs

Register

R

R

L

Register Files

2n

RE

WE

C RA(n)

WA(n)

MUX

Comparator

F Barrel shifter

Inputs

COE

< = >

Data busses Data

busses

Tri-buffer

S

Example 1: Datapath design (1)

Algorithm :

input sum;

FOR i = 1 TO 5

input x;

sum = sum + x;

ENDFOR

outport sum;

Temporary storage:

sum  Register

Functional units:

> 5  Comparator

• Each variable and constant corresponds to a register or counter

• Each operator corresponds to a functional unit.

Example 1: Datapath design (2)

input sum;

FOR i = 1 TO 5

input x;

sum = sum + x;

ENDFOR

outport sum;

• Connect outputs of registers and counter to input of functional units

• Connect output of functional units to input of registers and counter

Register x

Register sum

Up Counter

i

Register

= 5

L

5

1

Input

1

2 4

3

S

U

5

Example 1: Controller design

Input sum;

FOR i = 1 TO 5

input x;

sum = sum + x;

ENDFOR

outport sum;

State A

1 = 0  k0

State B

1 =0 2

State C

1 =1 4

3

State D

1 =1 2

State E

1 =1 5

C 1State F=1 6

0

1

Start=1 Start=0

1 2 3 4 5 6

Start

C

Clk Controller

One-hot FSM

 D-FF design

Example 2: FSMD Design

Thiết kế Datapath cho FSMD thực hiện thuật toán đếm và tính tổng của

các số lớn hơn 10 trong các số x đựơc đưa vào như sau:

cnt=0; sum=0;

Repeat

input x

if (x> 10) then

cnt=cnt + 1; sum=sum + x;

end if;

until x =0;

output sum; output cnt;

Chú ý: 1 0 ≤ x ≤255, 0≤ sum ≤255

Các lệnh viết trên cùng 1 hàng được thực hiện song song

2 Chỉ rõ các thanh ghi trong datapath là bao nhiêu bit