Register Descriptions; Bus Width Control Register (Abwcr) - Renesas H8S/2633 Series Hardware Manual

7.2

Register Descriptions

7.2.1

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.
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 5
to 7, and to H'00 in mode 4. It is not initialized by a manual reset or 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 Description
0 Area n is designated for 16-bit access
1 Area n is designated for 8-bit access
170
7 6 5
ABW6 ABW5
1 1 1
R/W R/W
0 0 0
R/W R/W
4 3
ABW4 ABW3 ABW2
1 1
R/W R/W R/W
0 0
R/W R/W R/W
2 1 0
ABW1 ABW0
1 1 1
R/W R/W
0 0 0
R/W R/W
(n = 7 to 0)