SHIFT REGISTER
SERIAL COMMUNICATION
System Digital
1
POKOK BAHASAN

Shift Registers
Definisi
 Model I/O : Serial, Pararel dan Kombinasi
 Arah pergeseran : Kiri, Kanan dan dua arah
 Applikasi/penggunaan
 Implementasi VHDL
Q
Q

3
MSI Shift Registers
 Komunikasi Serial

Input
D
Q
D
Q
Q1
2
D
Q
D
Q0
Q
Output
Clock
Enable
2
SHIFT REGISTERS
3
Memanfaatkan register untuk penyimpanan,
manipulasi dan transfer (pemindahan) data
DEFINISI

Register adalah sebuah rangkaian digital dengan dua
(2) fungsi utama : Data storage dan Data Movement
Shift register menyediakan fungsi data movement
 A shift register “shifts” its output once every clock cycle


Shift register adalah sekelompok flip flop yang
dipasang secara linier dengan masukan dan keluaran
saling disambungkan satu dengan yang lain, sehingga
data akan digeser dari satu alat ke alat yang lain
ketika rangkaian tersebut diaktifkan
4
PEMANFAATAN SHIFT REGISTER

Komunikasi

UART -> Universal
asynchronous
receiver/transmitter
Konversi antara serial
dan pararel
 Penyimpanan
sementara di
processor




Applikasi counter
Johnson counter
 ring counter
 LSFR counters

time delay devices
 more …

scratch-pad memories
Operasi Aritmatika

Perkalian, pembagian
5
SHIFT REGISTER CHARACTERISTICS

Tipe






Serial-in, Serial-out
Serial-in, Parallel-out
Parallel-in, Serial-out
Parallel-in, Parallel-out
Universal
Arah
n-bit shift
register
Left shift
 Right shift
 Rotate (right or left)
 Bidirectional

6
DATA MOVEMENT

Bit – bit dalam shift register dapat digeser sesuai
gambar dibawah ini
7
DATA MOVEMENT

Blok diagram shift register dengan berbagai variasi
input/output
n-bit shift
register
n-bit shift
register
n-bit shift
register
n-bit shift
register
8
SERIAL-IN SERIAL-OUT
Bit data masuk satu
persatu dan keluar satu
per satu
 Satu flip flop bertugas
untuk menyimpan satu
data
 Pergerakan data dapat
geser kiri / kanan, pada
umumnya satu register
hanya bisa satu arah.
 Masukan Asynchronous
preset dan clear digunakan
untuk set nilai awal

n-bit shift
register
9
SERIAL-IN SERIAL-OUT

Rangkaian logika ini menunjukkan gambar secara
umum Serial in Serial Out Shift Register



Menggunakan SR Flip Flop
Dirangkai sehingga memiliki perilaku seperti flip-flop D
Nilai masukan input akan digeser ke setiap flip-flop
berpadanan dengan clock pulse
N
1
0
N-Bit Shift Register
10
SHIFT REGISTERS





Shift register paling sederhana hanya menggunakan flip-flops
Keluaran dari flip-flop disambungkan dengan masukan D pada flipflop berikutnya di sebelah kanan
Setiap pulsa clock akan menggeser nilai register satu bit satu posisi
ke sebelah kanan
Serial input (SI) menentukan status masukan Flipflop paling kiri pada
saat terjadinya pergeseran, Serial output (SO) diambil dari keluaran
flipflop paling kanan
Perhatikan animasi
Q
Q
Q
Q
11
SERIAL-IN SERIAL-OUT
Cara paling mudah untuk
mempelajari adalah lihat
ilustrasi pada sebelah
kanan
 4 bit data word “1011” akan
di geser pada 4 bit shift
register
 One shift per clock pulse
 Data di tunjukkan masuk
dari sisi sebelah kiri dan
keluar dari sisi kanan

1
2
3
4
12
5
SERIAL-IN SERIAL-OUT
Diagram di sebelah
kanan menunjukkan
urutan 4 bit “1010” di
load ke 4 bit SISO shift
register
 Setiap bit akan
bergeser 1 posisi ke
sebelah kanan pada
setiap terjadi clock
leading edge
 dibutuhkan 4 pulsa
clock untuk
memasukkan seluruh
bit ke register.

13
SERIAL-IN SERIAL-OUT
Diagram disebelah
kanan menunjukkan
urutan 4 bit “1010”
unloaded dari 4 bit
SISO shift register
 Setiap bit akan
bergerak satu bit ke
kanan setiap signal
clock
 Dibutuhkan 4 clock
untuk mengakhiri
proses tersebut.

14
SERIAL-IN SERIAL-OUT

SISO di pergunakan
untuk komunikasi data
:





RS-232
modem transmission
and reception
Ethernet links
SONET
etc.
15
SERIAL-IN SERIAL-OUT IN VHDL

Berikut ini adalah kode program implementasi VHDL untuk
8 bit shift register pada positif edge clock Serial in Serial Out
library ieee;
use ieee.std_logic_1164.all;
entity shift is
port(C, SI : in std_logic;
SO : out std_logic);
end shift;
architecture archi of shift is
signal tmp: std_logic_vector(7 downto 0);
begin
process (C)
begin
if (C'event and C='1') then
for i in 0 to 6 loop
tmp(i+1) = tmp(i);
end loop;
tmp(0) = SI;
end if;
end process;
SO = tmp(7);
16
end archi;
KONVERSI SERIAL-TO-PARALLEL

Konversi serial ke pararel
dibutuhkan pada saat

Misal setelah menerima
transmisi data secara serial
n-bit shift
register
Ilustrasi 4 bit serial in
pararel out Shift register di
gambarkan di sebelah
kanan
 Output Q pada flipflop
paling kanan juga dapat
berfungsi sebagai serial out.

17
SERIAL-TO-PARALLEL CONVERSION
Digunakan serial in
pararel out shift
register sepanjang N
untuk mengubah N bit
word dari serial ke
pararel.
 Di butuhkan pulsa N
clock untuk load dan 1
clock pulse untuk
unload

18
SERIAL-TO-PARALLEL CONVERSION
Dua buah shift
register di sebelah
kanan digunakan
konversi serial data
ke pararel data
 Register bagian
bawah akan
menyediakan untuk
register bagian atas,
ketika di geser oleh
register bag bawah

19
PARALLEL-TO-SERIAL CONVERSION
Data di applikasikan ke bentuk
pararel, kemudian di umpan
masukkan ke Pin A hingga D.
 Kemudian dibaca secara
sequential pada register 1 bit
pada satu waktu dari PA ke PD
setiap 1 siklus clock dalam
bentuk serial
 Satu pulsa clock untuk load
 Empat pulsa clock untuk
unload

n-bit shift
register
20
PARALLEL-TO-SERIAL CONVERSION

Logic circuit for a parallel-in, serial-out shift register
0
1
0
1
0
Mux-like
1
21
PARALLEL-IN PARALLEL-OUT
Parallel-in Parallel-out
Shift Registers can serve
as a temporary storage
device or as a time delay
device
 The DATA is presented in
a parallel format to the
parallel input pins PA to
PD and then shifted to the
corresponding output pins
QA to QD when the
registers are clocked
 One clock pulse to load
 One pulse to unload

22
UNIVERSAL SHIFT REGISTER
Universal shift register
 Can do any combination of
parallel and serial
input/output operations
 Requires additional inputs
to specify desired function
 Uses a Mux-like input
gating

n-bit shift
register
L/S
L/S
A
0
B
1
F
A
B
0
1
23
UNIVERSAL SHIFT REGISTER

Parallel-in, parallel-out shift register
0
1
0
1
0
Mux-like
1
24
UNIVERSAL SHIFT REGISTER

Parallel shift register (can serve as converting
parallel-in to serial-out shifter):
25
MSI SHIFT REGISTERS
74LS164 is an 8-Bit
Serial-In Parallel-Out
Shift Register
 Typical Shift Frequency
of 35 MHz
 Asynchronous Master
Reset
 Gated Serial Data Input
 Fully Synchronous Data
Transfers

26
MSI SHIFT REGISTERS

74LS164 8-Bit Serial-In Parallel-Out Shift Register
27
MSI SHIFT REGISTERS
The 74LS164 is an edge-triggered 8bit shift register with serial data
entry and an output from each of
the eight stages.
 Data is entered serially through one
of two inputs (A or B);



either of these inputs can be used as
an active HIGH Enable for data entry
through the other input
an unused input must be tied HIGH,
or both inputs connected together
28
MSI SHIFT REGISTERS
Each LOW-to-HIGH transition on
the Clock (CP) input shifts data one
place to the right
 This also enters into Q0 the logical
AND of the two data inputs (A•B)
that existed before the rising clock
edge.

29
MSI SHIFT REGISTERS

74LS164 logic diagram
A LOW level on the Master Reset (MR) input overrides all other
inputs and clears the register asynchronously, forcing all Q outputs
LOW.
30
MSI SHIFT REGISTERS
74LS166 is an 8-Bit
Shift Register
 Parallel-in or serial-in


shift/load input
establishes the parallel-in
or serial-in mode
Serial-out
 Synchronous Load



Serial data flow is
inhibited during parallel
loading
Direct Overriding Clear
31
MSI SHIFT REGISTERS

74LS166 is an 8-Bit Shift Register
32
MSI SHIFT REGISTERS

74LS166 8-Bit Shift Register is a parallel-in or
serial-in, serial-out shift register
33
MSI SHIFT REGISTERS

74LS166 is an 8-Bit Shift
Register
34
MSI SHIFT REGISTERS

74LS166 is an 8-Bit Shift Register
35
MSI SHIFT REGISTERS
74LS194 4-Bit
Bidirectional Universal
Shift Register
 may be used in








serial-serial,
shift left,
shift right,
serial-parallel,
parallel-serial,
and parallel-parallel
data register transfers
36
MSI SHIFT REGISTERS

74LS194 4-Bit Bidirectional Universal Shift
Register
37
MSI SHIFT REGISTERS

74LS194 control inputs S1 and S0
38
MSI SHIFT REGISTERS

74LS194 4-Bit Bidirectional Universal Shift
Register
01
11
10
00
01
11
10
00
01
11
10
00
01
11
10
00
39
MSI SHIFT REGISTERS

74LS194 4-Bit Bidirectional Universal Shift
Register
40
“UNIVERSAL”
SHIFT
REGISTER
74X194
Shift left
 Shift right
 Load
 Hold

41
MSI SHIFT REGISTERS

One stage of the 74x194
42
VHDL DHIFT REGISTER
Universal shift
register design
 The 3-bit
function select
determines the
operation of
the register
 Serial in and
Parallel load
available

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_unsigned.all;
entity Vshftreg is
port (CLK, CLR, RIN, LIN: in STD_LOGIC;
S: in STD_LOGIC_VECTOR (2 downto 0); -- function select
D: in STD_LOGIC_VECTOR (7 downto 0); -- data in
Q: out STD_LOGIC_VECTOR (7 downto 0) -- data out);
end Vshftreg;
architecture Vshftreg_arch of Vshftreg is
signal IQ: STD_LOGIC_VECTOR (7 downto 0);
begin
process (CLK, CLR, IQ)
begin
if (CLR='1') then IQ <= (others=>'0');
elsif (CLK'event and CLK='1') then
case CONV_INTEGER(S) is
when 0 => null;
when 1 => IQ <= D;
when 2 => IQ <= RIN & IQ(7 downto 1);
when 3 => IQ <= IQ(6 downto 0) & LIN;
when 4 => IQ <= IQ(0) & IQ(7 downto 1);
when 5 => IQ <= IQ(6 downto 0) & IQ(7);
when 6 => IQ <= IQ(7) & IQ(7 downto 1);
when 7 => IQ <= IQ(6 downto 0) & '0';
when others => null;
end case;
end if;
Q <= IQ;
end process;
end Vshftreg_arch;
---------
Hold
Load
Shift
Shift
Shift
Shift
Shift
Shift
right
left
circular right
circular left
arithmetic right
arithmetic left
43
MSI SHIFT REGISTERS
74LS299 is an 8-bit
universal shift/storage
register with 3-state
outputs
 Four modes of operation
are possible:





hold (store)
shift left
shift right
load data
44
MSI SHIFT REGISTERS

74LS299 universal shift/storage register
45
MSI SHIFT REGISTERS

74LS299 universal shift/storage register
S0
S1
D
Q
CP
CD
46
MSI SHIFT REGISTERS

74LS299 logic circuit diagram:
The parallel load inputs and flip-flop outputs are multiplexed
to reduce the total number of package pins.
 Separate outputs are provided for flip-flops Q0 and Q7 to
allow easy cascading.
 A separate active LOW Master Reset is used to reset the
register.

47
SERIAL COMMUNICATIONS
48
A practical application of Registers / Shift Registers
SERIAL DATA SYSTEMS (E.G., TPC)

Read discussion and study circuits in text.
49
SERIAL DATA TRANSMISSION

Parallel-to-serial conversion for serial transmission
out: parallel data
in: parallel data
Source module
Destination module
serial transmission media
50
SERIAL DATA IN THE PHONE SYSTEM (E-1)

2.048 Mb/s links between phone switches and
subscribers


partitioned into 32 64 Kb/s channels
Each channel gets a timeslot in a “frame” where
it can send 8 bits every 125 sec.

8000 frames/sec
51
TIMESLOT
DETAILS
count = 255
52
256
PARALLEL-TOSERIAL CONVERSION
LSBs are bit number
Assert shift-register
LOAD input during bit 7
Timeslot number can
be decoded and used
to select source of
parallel data
count = 255
Serial data to
destination
53
Synchronize
destination’s
counter to
source’s
Note:
loads
0…0
Shift in serial data
SERIAL-TOPARALLEL
CONVERSION
Detect that a
complete byte
has been
received
Holding register
for complete
byte
54
DESTINATION TIMING
Grab complete byte when available
Holding-register outputs
Serial-in, parallel-out
shift register outputs
55
SERIAL COMMUNICATION ON ONE WIRE
Serial communication requires three signals:
CLOCK, SYNC, and DATA. Yet only one “wire” is
used. How?
 One solution: Manchester code.

• Or use a phase-locked loop (analog circuit)
to extract clock from the data:
56
STILL A COUPLE OF PROBLEMS

Framing -- SYNC signal


Solution: Use a unique data pattern for SYNC
PLL clock recovery -- what if too many zeroes are
transmitted? PLL can’t stay in sync.
Solution: Use a code that guarantees a minimum
number of ones
 Phone system: Map 00000000 --> 00000010 (creating
slight voice distortion)


Gigabit Ethernet: Uses 8B10B code, solving both
problems
Map each byte into 8 bits
 Use only a “good” subset of 210 code words
 Use another code word for synchronization

57
ASSIGNMENTS


Completed Part 2 Midterm problems due
Wednesday
Continue working on the MIPS project

Description available on the course web page
58