Register Descriptions; Bus Width Control Register (Abwcr) - Hitachi H8S/2338 Series Hardware Manual

4.2

Register Descriptions

4.2.1

Bus Width Control Register (ABWCR)

Bit :
ABW7
Modes 5 to 7
Initial value :
R/W : R/W
Mode 4
Initial value :
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 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.
Note: * Modes 6 and 7 are not provided in the ROMless version.
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
50
7 6
ABW6 ABW5
1 1
R/W R/W
0 0
R/W R/W
5 4
ABW4 ABW3
1 1
R/W R/W
0 0
R/W R/W
3 2
ABW2 ABW1
1 1
R/W R/W
0 0
R/W R/W
1 0
ABW0
1 1
R/W
0 0
R/W
(n = 7 to 0)