117
Chapter 4
Bus Control Function
Preliminary User’s Manual U15839EE1V0UM00
4.6.3 Endian
control
function
The endian control function can be used to set processing of word data in memory either by the Big
Endian method or the Little Endian method for each CS area selected with the chip select signal (CS0
to CS7). Switching of the endian method is specified with the endian configuration register (BEC).
(1)
Endian configuration register (BEC)
This register can be read/written in 16-bit units.
Cautions: 1. Bits 15, 13, 11, 9, 7, 5, 3, and 1 of the BEC register must be cleared (0). If these bits
are set to 1, the operation is not guaranteed.
2. Set the CSn area specified as the programmable peripheral I/O area to Little
Endian format (n = 0 to 7).
3. In the following areas, the data processing method is fixed to Little Endian
method. Any setting of Big Endian method for these areas according to the BEC
register is invalid.
- On-chip peripheral I/O area
- Internal RAM area
- Fetch area of external memory
Figure 4-5:
Big Endian Addresses within Word
Figure 4-6:
Little Endian Addresses within Word
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Address
Initial
value
BEC
0
BE70
0
BE60
0
BE50
0
BE40
0
BE30
0
BE20
0
BE10
0
BE00 FFFFF068H
0000H
CS7
CS6
CS5
CS4
CS3
CS2
CS1
CS0
Bit Position
Bit Name
Function
14, 12, 10, 8,
6, 4, 2, 0
BEn0
(n = 0 to 7)
Big Endian
Specifies the endian method.
BEn0
Endian Control
0
Little Endian method
1
Big Endian method
0008H
0009H
000AH
000BH
0004H
0005H
0006H
0007H
0000H
0001H
0002H
0003H
31
24 23
16 17
8 7
0
000BH
000AH
0009H
0008H
0007H
0006H
0005H
0004H
0003H
0002H
0001H
0000H
31
24 23
16 17
8 7
0
Summary of Contents for mPD703128
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