1. Serial versus Parallel Data Transfers
OUTLINE:
Shift Registers
Converting data from Serial  Parallel
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

2. Tim Sumner, Imperial College, Rm: 1009, x47552
Shift Registers
Shift Registers convert numbers expressed in terms of several bits
(many signal lines) into a stream
of 0, 1 and a Clock.
Advantage: A convenient way to reduce the number of
Electrical signal lines by factors of 8, 16, 32, 64.
Disadvantage: For the same transfer rate the electronics must be faster by factors of 8, 16, 32, 64.
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

3. What do Shift Registers Do ?
$AA D7 H D6 L D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 H L
4 DFF
Data_in
Data_out
Set Up
Clock
Set Up
Set Up
Set Up
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

4. Tim Sumner, Imperial College, Rm: 1009, x47552
Suppose you feed an ‘1’: D0 D1 D2 D3 D4 D5 D6 D7 1 T 2T 3T 4T 5T 6T 7T 8T
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

5. Tim Sumner, Imperial College, Rm: 1009, x47552
The 74HC165 Shift Register
Serial Data In
Serial Data
Out
8-bit Word
Clock
*Load
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

6. Tim Sumner, Imperial College, Rm: 1009, x47552
The 74HC165 data
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Tim Sumner, Imperial College, Rm: 1009, x47552

7. Tim Sumner, Imperial College, Rm: 1009, x47552
The 74HC164 Shift Register
Serial Data In
Parallel
out
Clock
*Load
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

8. Parallel becomes Serial
High Level Design
Parallel becomes Serial
We want to construct :
8-Bits of data
(Parallel)
ATmega103
Board
Shift
Register
74HC165
Serial Data
PORTB
Clock
Shift/*Load
Shift
Register
74HC164
PORTC
Serial
to Parallel
Clock
8-Bits of data
(Parallel)
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

9. Tim Sumner, Imperial College, Rm: 1009, x47552
Low Level Design
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

10. The Memory Test Program
Start
Shift 8 times
Select new pattern
Clock the 165
using PORTC
Delay several seconds
Look at
the LEDs
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

11. Tim Sumner, Imperial College, Rm: 1009, x47552
Task Plan:
Construct a device that will turn 8-bit
parallel data from Port-B to serial data
+ clock .
(2) Construct a device that will receive
serial data, convert them to parallel
data and display them using LEDs.
(3) Write a program that will send several
patterns down your ‘serial link’ and
demonstrate that it works.
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

12. For more motivated students:
You can attempt storing your data in a register at the end before sending them to the LEDs.
This will require knowledge on how a register really works
Next few slides describe the 75HC574 register with 3-state outputs.
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

13. Guess what is the 1 Byte memory ?
It exists in one package : E
DAT-7
Q-7      
74F574
Byte coming in
Byte Stored
Q-0
DAT-0
CLK
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

14. Tim Sumner, Imperial College, Rm: 1009, x47552
The data sheets of the 74F574
Register
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

15. Tim Sumner, Imperial College, Rm: 1009, x47552
What does the 74F574 do ?
The outputs of the 574 are tri-state : They
Can be high ‘1’, low ‘0’, and DISCONNECTED
(HIGH IMPEDANCE STATE).
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552

16. Tim Sumner, Imperial College, Rm: 1009, x47552
The 74F574 Truth Table
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Tim Sumner, Imperial College, Rm: 1009, x47552

17. The Data Sheets of the 74F574 I
Register ts C2
DataIn
tPZH
EN1
DataOut
Ts = setup time
tPZH = Output Enable time
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Tim Sumner, Imperial College, Rm: 1009, x47552

18. The Data Sheets of the 74F574 IIC2
DataIn
EN1
DataOut tp
Tp = propagation delay
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Tim Sumner, Imperial College, Rm: 1009, x47552

19. Tim Sumner, Imperial College, Rm: 1009, x47552
Task II:
Construct the following circuit:
Make sure that after clocking the serial data eight times you also clock the data in to the register.
22/11/2018
Tim Sumner, Imperial College, Rm: 1009, x47552