9/15/09 - L26 Shift Registers Copyright 2009 - Joanne DeGroat, ECE, OSU 1

Shift Registers

9/15/09 - L26 Shift Registers Copyright 2009 - Joanne DeGroat, ECE, OSU 2

Class 25 – Shift Registers Multiplication by 2 (division by 2) Shift Register topology

Material from section 7-6 of text

Effect of a shift operation A single shift is multiplication by 2 Consider the operation 6 x 2 = 12

0110 x 0010 0000 0110 . Will skip last 2 rows of terms of 0s 01100

Note that this result is just a shift by 1 position.

9/15/09 - L26 Shift Registers Copyright 2009 - Joanne DeGroat, ECE, OSU 3

Multiplication by shift Reference base 10. To multiply or divide by 10 you

just move the decimal point, or in scientific notation, adjust the exponent.

In base 2 you can move the binary point Right by 1 position to multiply by 2 Left by 1 position to divide by 2

Or shift the binary number on a fixed binary point Left by 1 position to multiply by 2

1110. x 2 11100. Right by 1 position to divide by 2

11100. 2 1110.

9/15/09 - L26 Shift Registers Copyright 2009 - Joanne DeGroat, ECE, OSU 4

A 4-bit shift register Shift word one bit each clock. Sometimes called a FIFO or First in First Out

across all the bits of the word.

9/15/09 - L26 Shift Registers Copyright 2009 - Joanne DeGroat, ECE, OSU 5

SR with Parallel Load Shift Register with

Parallel Load

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Bidirectional Shift Register Also have load

operation Representation

is only partial Note the serial

input and output

9/15/09 - L26 Shift Registers Copyright 2009 - Joanne DeGroat, ECE, OSU 7

Operations allowed Several operations supported

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The mux in from of each F/F The multiplexer in front of each flip flop

routes the selected input to the FF input. The current FF output The less significant FF output (or serial in-lsb) The most significant FF output (or serial out-

msb) A new input to load.

9/15/09 - L26 Shift Registers Copyright 2009 - Joanne DeGroat, ECE, OSU 9

The look The register setup Note that all signal

routing is not shown.

9/15/09 - L26 Shift Registers Copyright 2009 - Joanne DeGroat, ECE, OSU 10

Class 25 assignment Covered part of section 7-6 Problems for hand in

Nothing new Problems for practice

Nothing new

Reading for next class: counters from 7-6

9/15/09 - L26 Shift Registers Copyright 2009 - Joanne DeGroat, ECE, OSU 11