Lecture-7

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Digital Logic Design
Lecture – 7:
Shift registers
Konakbayev Olzhas

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Lecture base
Digital Electronics: Principles & Applications, 9th edition by Roger
Tokheim & Patrick E. Hoppe:
• Chapter 9
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Introduction
• Overview of Shift Registers
• Characteristics of Shift Registers
• Serial/Parallel Data Conversion
• Serial Load Shift Register
• Parallel Load Shift Register
• Recirculating Shift Register
• A Universal Shift Register
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Overview of Shift Registers 1
A shift register is a sequential logic device made up of
flip-flops that allows parallel or serial loading and serial
or parallel outputs as well as shifting bit by bit.
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Overview of Shift Registers 2
Common tasks of shift registers:
• Serial/parallel data conversion
• UART = Universal Asynchr. Receiver/transmitter (an
example)
• Time delay
• Ring counter
(https://en.wikipedia.org/wiki/Ring_counter)
• Twisted-ring counter or Johnson counter
(https://en.wikipedia.org/wiki/Ring_counter)
• Memory device
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Characteristics of Shift Registers 1
• Number of bits (4-bit, 8-bit, etc.)
• Loading
• Serial
• Parallel
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Characteristics of Shift Registers 2
• Common modes of operation
• Parallel load
• Shift right-serial load
• Shift left-serial load
• Hold
• Clear
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Serial/Parallel Data Conversion
Shift registers can be used to convert from serial-toparallel or the reverse from parallel-to-serial.
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Serial Load Shift Register
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Parallel Load Shift Register
• Serial-load shift registers permit only one bit of data to
be entered at a time.
• Serial-load shift registers lose the data out the right
side as it shifts right.
• Parallel-load shift registers permit all four bits of data
to be entered at a time.
• Parallel-load shift registers can incorporate a
recirculating feature that brings the output data back
into the input so they are not lost.
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Recirculating Shift Register 1
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Recirculating Shift Register 2
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A Universal Shift Register 1
Semiconductor manufacturers produce shift registers in
IC form. An example is the 74LS194 4-bit bidirectional
universal shift register.
• Shift right
• Shift left
• Serial load
• Parallel load
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A Universal Shift Register 2
Serial-load shift-right reg.
Serial-load shift-left reg.
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A Universal Shift Register 3
Parallel-load shift-right/left register
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Review 1
What type of shift register is shown below?
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Review 2
What type of shift register is shown below?
Serial in-serial out
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Review 3
What type of shift register is shown below?
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Review 4
What type of shift register is shown below?
Serial in-parallel out
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Review 5
What type of shift register is shown below?
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Review 6
What type of shift register is shown below?
Parallel in-serial out
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Review 7
What type of shift register is shown below?
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Review 8
What type of shift register is shown below?
Parallel in-parallel out
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Review 9
List the Common modes of operation of a shift register
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Review 10
List the Common modes of operation of a shift register
• Parallel load
• Shift right-serial load
• Shift left-serial load
• Hold
• Clear
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Review 11
• ___________ shift registers permit only one bit of
data to be entered at a time.
• ___________ shift registers lose the data out the right
side as it shifts right.
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Review 12
• Serial-load shift registers permit only one bit of data to
be entered at a time.
• Serial-load shift registers lose the data out the right
side as it shifts right.
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Review 13
• ____________ shift registers permit all four bits of
data to be entered at a time.
• ____________ shift registers can incorporate a
recirculating feature that brings the output data back
into the input so they are not lost.
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Review 14
• Parallel-load shift registers permit all four bits of data
to be entered at a time.
• Parallel-load shift registers can incorporate a
recirculating feature that brings the output data back
into the input so they are not lost.
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Thank you!
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