8/13/2019 Big Indian Little Indian

1/1

1 09/16/99

1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3

1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3

Application Brief AB-32

1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2

1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 1 2 3 4 5 6 7 8 9 0 1 2

Big Endian to Little Endian Data ConversionUsing 3.3V Bus Switches

by Refugio Jones August 18, 1999

Byte order storage can significantly impact the compatibility be-

tween devices within and outside of a system. The order in which

data is stored into memory varies according to the application at

hand. Big Endian and Little Endian describe the order or sequence

in which multi-byte data is stored in memory.

Little Endian specifies that the least significant byte is stored in

the lowest memory address. The Intel PentiumTM

and Compaq/DecAlphaTMprocessors are Little Endian. In turn, Big Endian format-

ting takes the most significant byte and stores it in the lowest

memory address (see Figure 1). The Motorola 680x0 and Sun

SuperSPARCTMare Big Endian.

Figure 1. Big Endian vs. Little Endian Memory Formatting

Application Brief AB34

Introduction Application Description

Often, based on the application, it is required to convert Big Endian

into Little Endian formatting or visa versa. Figure 2 show how

Pericoms 3.3V Mux/Demux Bus Switches can be used to perform

the required conversion.

In the example, the PI3B16233 is a bidirectional device and can be

easily controlled to convert from one format to the other.

Given a double word that is located on the input of the A ports, thePI3B16233 can Mux the word over the B side in the desired order

(see Figure 2.)

DOUBLE WORD (32-BIT) IN LITTLE-ENDIAN FORMATBITS 0-7

31 23 15 724

M+3 M+2 M+1 M

16 8 0

DOUBLE WORD (32-BIT) IN BIG-ENDIAN FORMAT

M = Most Significant Memory Location or Word

31 23 15 724

M M+1 M+2 M+3

16 8 0

Intel CPU

Little Endian

(Low Order Byte At

Starting Address)

M3

M1

M0

M2

M3

D24 - D31

D16 - D23

D8 - D15

D0 - D7

M2

M3

M2

8

8

8

8

M1

M0

MotorolaCPU

PI3B16233

PI3B16233

M0

M2

M3

M1

M1

M0

M3

M2

Big Endian

(High Order Byte At

Starting Address)

Memory

Figure 2. Converting Between Big Endian and Little Endian