CHAPTER 4 BCU
Preliminary User’s Manual A14874EJ3V0UM
86
4.5 Bus Size Setting Function
The bus size setting function uses the bus size configuration register (BSC) to set the VSB data bus size for each
CSn area selected by the chip select signals (VDCSZn) (see
Figures 4-3
and
4-4
) (n = 7 to 0).
The BSC register can be read or written in 16-bit units.
Figure 4-7. Bus Size Configuration Register (BSC)
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
BSC
BS
71
BS
70
BS
61
BS
60
BS
51
BS
50
BS
41
BS
40
BS
31
BS
30
BS
21
BS
20
BS
11
BS
10
BS
01
BS
00
Address
FFFFF066H
After reset
Note
Bit position
Bit name
Function
Specifies the peripheral macro on the VSB that was located in the CSn area and the data bus
size.
BSn1
BSn0
VSB data bus size
0
0
8 bits
0
1
16 bits
1
0
32 bits
1
1
Setting prohibited
15 to 0
BSn1,
BSn0
Remark
n = 7 to 0
Note
The after-reset value differs as follows according to the input levels to the IFINSZ1 and IFINSZ0 pins.
IFINSZ1
IFINSZ0
VSB data bus size
After-reset value
Low level
Low level
32 bits
AAAAH
Low level
High level
16 bits
5555H
High level
Low level
8 bits
0000H
Example
In a CSn area, when the boot ROM is 16-bit width and memories in other areas are 32-bit width, start up
using 16-bit width in the initial state (input a low level to the IFINSZ1 pin and a high level to the IFINSZ0
pin) and then switch to 32-bit width via the BSC resister.