HD6432633 Datasheet, PDF (224/1453 Pages) Renesas Technology Corp – Series of Microcomputers (MCUs: microcomputer units)

7.2 Register Descriptions
7.2.1 Bus Width Control Register (ABWCR)
Bit
:
Modes 5 to 7
Initial value :
R/W
:
Mode 4
Initial value :
R/W
:
7
6
5
4
3
2
1
0
ABW7 ABW6 ABW5 ABW4 ABW3 ABW2 ABW1 ABW0
1
1
1
1
1
1
1
1
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
ABWCR is an 8-bit readable/writable register that designates each area for either 8-bit access or
16-bit access.
ABWCR sets the data bus width for the external memory space. The bus width for on-chip
memory and internal I/O registers is fixed regardless of the settings in ABWCR.
In normal mode, the settings of bits ABW7 to ABW1 have no effect on operation.
After a power-on reset and in hardware standby mode, ABWCR is initialized to H'FF in modes 5
to 7, and to H'00 in mode 4. It is not initialized by a manual reset or in software standby mode.
Bits 7 to 0—Area 7 to 0 Bus Width Control (ABW7 to ABW0): These bits select whether the
corresponding area is to be designated for 8-bit access or 16-bit access.
Bit n
ABWn
0
1
Description
Area n is designated for 16-bit access
Area n is designated for 8-bit access
(n = 7 to 0)
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