Page 196 - DCAP108_DIGITAL_CIRCUITS_AND_LOGIC_DESIGNS

Unit 11: Registers and Counters

Notes
Table 11.4: The Register Performs Right Shift Operation

Q 0 Q 1 Q 2 Q 3
Clear 0 0 0 0
Write 1 0 0 1
Shift 1 0 0 1
1 1 0 0 1
1 1 1 0 01
1 1 1 1 001
1 1 1 1 1001

8-bit Parallel-Load Shift Register (74HC165)
The 74HC165 is an example of an IC shift register that has a parallel-in/serial-out operation.
It can also be operated as serial-in/serial-out. Figure 11.11 shows the logic diagram and logic
symbol of 74HC165.
Figure 11.11: The Logic Diagram and Logic Symbol of 74HC165
Parallel inputs

D 0 D 1 D 2 D 3 D 4 D 5 D 6 D 7
(11) (12) (13) (14) (3) (4) (5) (6)

S S S S S S S S (9)
Output
Q
C C C C C C C C 7
(10) (7)
D D D D D D D D
SER R R R R R R R R Output
Q 7
(1)
SH/LD

CLK
(2)
(5)
() Logic diagram
a
CLK INH
D 0 D 1 D 2 D 3 D 4 D 5 D 6 D 7

(11) (12) (13) (14) (3) (4) (5) (6)
(1) (9)
SHILD Q
(10) SRG 8 7
SER
(15)
CLK INH
(2) (7)
CLK C Q
7
() Logic symbol
b

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