HD6432646 Hitachi, HD6432646 Datasheet - Page 178

• Manufacturer Part Number: HD6432646
• Description: (HD64F264x Series) 16-Bit Microcomputer
• Manufacturer: Hitachi

7.2
7.2.1
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.
After a reset and in hardware standby mode, ABWCR is initialized to H'FF in modes 5, 6, 7, and
to H'00 in mode 4. It is not initialized 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
7.2.2
ASTCR is an 8-bit readable/writable register that designates each area as either a 2-state access
space or a 3-state access space.
144
Bit
Initial value
R/W
Bit
Modes 5 to 7
Initial value :
RW
Mode 4
Initial value :
RW
Register Descriptions
Bus Width Control Register (ABWCR)
Access State Control Register (ASTCR)
Description
Area n is designated for 16-bit access
Area n is designated for 8-bit access
:
:
:
:
:
:
ABW7
AST7
R/W
R/W
R/W
7
1
7
1
0
ABW6
AST6
R/W
R/W
R/W
6
1
6
1
0
ABW5
AST5
R/W
R/W
R/W
5
1
5
1
0
ABW4
AST4
R/W
R/W
R/W
4
1
4
1
0
ABW3
AST3
R/W
R/W
R/W
3
1
3
1
0
ABW2
AST2
R/W
R/W
R/W
2
1
2
1
0
ABW1
AST1
R/W
R/W
R/W
1
1
1
1
0
(n = 7 to 0)
ABW0
AST0
R/W
R/W
R/W
0
1
0
1
0