Memory Interface

Big Endian

Memory

 

0 1 2 3 4 5 6 7

00a 0b 0c 0d 0e 0f

801 02 03 04 05 06 07 08

16 ($10) 11 22 33 44 cc dd ee ff

24($18)

32($20)

Little Endian

7

6

5

4

3

2

1

0

0f 0e 0d 0c 0b 0a

07 08 05 06 03 04 01 02

cc dd ee ff 11 22 33 44

0

8

16($10)

24($18)

32($20)

Instructions

Data Bus Contents

MOVE.B (A0), D0

xxxx xxxx xxxx xx0a

MOVE.B (A2), D0

xxxx xxxx xxxx xx0c

MOVE.W (A8), D0

xxxx xxxx xxxx 0102

MOVE.L (A16), D0

xxxx xxxx 1122 3344

 

 

XA-BUS

XB-BUS

 

 

 

 

64-bit

64-bit

 

 

 

 

SC140 Core

Figure 2-22. Data Transfer in Big and Little Endian Modes

For single-register moves, assuming an equivalent memory map in big and little endian modes, the byte organization on the buses is identical in both modes. However, the memory subsystem must route the data bus bytes to different memory addresses for each supported endian mode.

SC140 DSP Core Reference Manual

2-59

Page 91
Image 91
Freescale Semiconductor SC140 specifications Data Transfer in Big and Little Endian Modes