HD64F2357F20V Datasheet, PDF (138/1049 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-chip Microcomputer H8S Family / H8S/2300 Series

6.2 Register Descriptions
6.2.1 Bus Width Control Register (ABWCR)
Bit
:
Modes 5 to 7
Initial value :
R/W
:
7
ABW7
1
R/W
6
ABW6
1
R/W
5
ABW5
1
R/W
4
ABW4
1
R/W
3
ABW3
1
R/W
2
ABW2
1
R/W
1
ABW1
1
R/W
0
ABW0
1
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
0
1
Description
Area n is designated for 16-bit access
Area n is designated for 8-bit access
(n = 7 to 0)
Rev.6.00 Oct.28.2004 page 108 of 1016
REJ09B0138-0600H