Rev.6.00 Oct.28.2004 page 108
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REJ09B0138-0600H
6.2
Register Descriptions
6.2.1
Bus Width Control Register (ABWCR)
Bit
:
7
6
5
4
3
2
1
0
ABW7
ABW6
ABW5
ABW4
ABW3
ABW2
ABW1
ABW0
Modes 5 to 7
Initial value :
1
1
1
1
1
1
1
1
R/W
:
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Mode 4
Initial value :
0
0
0
0
0
0
0
0
R/W
:
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.
After a power-on reset and in hardware standby mode, ABWCR is initialized to H'FF in modes 5 to 7,*
1
and to H'00 in
mode 4. It is not initialized by a manual reset*
2
or in software standby mode.
Notes: 1. In ROMless version, modes 6 and 7 are not available.
2. Manual reset is only supported in the H8S/2357 ZTAT.
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
Description
0
Area n is designated for 16-bit access
1
Area n is designated for 8-bit access
(n = 7 to 0)
Содержание ZTAT H8S/2357F
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