HD6432621 Hitachi, HD6432621 Datasheet - Page 183

• Manufacturer Part Number: HD6432621
• Description: (HD64F262x 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 to 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
Bit
Modes 5 to 7
Initial value :
R/W
Mode 4
Initial value :
R/W
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
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