Datasheet

Section 6 Bus Controller
Rev.6.00 Sep. 27, 2007 Page 149 of 1268
REJ09B0220-0600
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 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
(n = 7 to 0)