H8S2245 datasheet(177/818 Pages) RENESAS

177 / 818 page

Section 6 Bus Controller

Rev.3.00 Mar. 26, 2007 Page 135 of 772

REJ09B0355-0300

6.2

6.2.1

Bus Width Control Register (ABWCR)

ABW7

R/W

ABW6

R/W

ABW5

R/W

ABW4

R/W

ABW3

R/W

ABW0

R/W

ABW2

R/W

ABW1

R/W

Bit

Modes 1, 2, 3, 5, 6, 7

Initial value

R/W

Mode 4

Initial value

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 1,

2, 3, and 5, 6, 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. In normal mode, only part

of area 0 is enabled, and the ABW0 bit selects whether external space is to be designated for 8-bit

access or 16-bit access.

Bit n

ABWn

Description

Area n is designated for 16-bit access

Area n is designated for 8-bit access

Note:

n = 7 to 0

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