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

6.2

Register Descriptions

6.2.1

Bus Width Control Register (ABWCR)

Bit : 7
ABW7
Modes 5 to 7
Initial value : 1
R/W : R/W
Mode 4
Initial value : 0
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,*
mode 4. It is not initialized by a manual reset*
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
0
1
Rev.6.00 Oct.28.2004 page 108 of 1016
REJ09B0138-0600H
6 5
ABW6 ABW5
1 1
R/W R/W
0 0
R/W R/W
2
or in software standby mode.
Description
Area n is designated for 16-bit access
Area n is designated for 8-bit access
4 3 2
ABW4 ABW3 ABW2
1 1 1
R/W R/W R/W
0 0 0
R/W R/W R/W
1 0
ABW1 ABW0
1 1
R/W R/W
0 0
R/W R/W
1
and to H'00 in
(n = 7 to 0)