HD6412350 Hitachi, HD6412350 Datasheet - Page 144

• Manufacturer Part Number: HD6412350
• Description: (HD6412350 / HD6432351) 16-BIT MICROCONTROLLER
• Manufacturer: Hitachi

6.2
6.2.1
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 1,
2, 3, and 5, 6, 7*, and to H'00 in mode 4. It is not initialized by a manual reset or in software
standby mode.
Note: * Modes 2, 3, 6 and 7 only apply to the H8S/2351.
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. In normal mode, only part
of area 0 is enabled, and the ABW0 bit selects whether external space is to be designated for 8-bit
access or 16-bit access .
Bit n
ABWn
0
1
124
Bit
Modes 1 to 3, 5 to 7*
Initial value :
RW
Mode 4
Initial value :
RW
Register Descriptions
Bus Width Control Register (ABWCR)
Description
Area n is designated for 16-bit access
Area n is designated for 8-bit access
:
:
:
ABW7
R/W
R/W
7
1
0
ABW6
R/W
R/W
6
1
0
ABW5
R/W
R/W
5
1
0
ABW4
R/W
R/W
4
1
0
ABW3
R/W
R/W
3
1
0
ABW2
R/W
R/W
2
1
0
ABW1
R/W
R/W
1
1
0
(n = 7 to 0)
ABW0
R/W
R/W
0
1
0