Register Configuration; Register Descriptions; Bus Width Control Register (Abwcr) - Hitachi H8/3008 Hardware Manual

6.1.4

Register Configuration

Table 6.2 summarizes the bus controller's registers.
Table 6.2 Bus Controller Registers
1
Address* Name
H'EE020 Bus width control register
H'EE021 Access state control register
H'EE022 Wait control register H
H'EE023 Wait control register L
H'EE013 Bus release control register
H'EE01F Chip select control register
H'EE01E Address control register
H'EE024 Bus control register
Notes: 1. Lower 20 bits of the address in advanced mode.
2. In modes 2 and 4, the initial value is H'00.
3. In modes 3 and 4, the initial value is H'EE.
6.2

Register Descriptions

6.2.1

Bus Width Control Register (ABWCR)

ABWCR is an 8-bit readable/writable register that selects 8-bit or 16-bit access for each area.
Bit
Modes
Initial value
1 and 3
Read/Write
Initial value
Modes
2 and 4
Read/Write
When ABWCR contains H'FF (selecting 8-bit access for all areas), the chip operates in 8-bit bus
mode: the upper data bus (D
bit is cleared to 0 in ABWCR, the chip operates in 16-bit bus mode with a 16-bit data bus (D
D ). In modes 1 and 3, ABWCR is initialized to H'FF by a reset and in hardware standby mode.
0
In modes 2 and 4, ABWCR is initialized to H'00 by a reset and in hardware standby mode. It is
not initialized in software standby mode.
102
7 6
ABW7 ABW6 ABW5
1 1
R/W R/W
0 0
R/W R/W
to D ) is valid, and port 4 is an input/output port. When at least one
15 8
Abbreviation
ABWCR
ASTCR
WCRH
WCRL
BRCR
CSCR
ADRCR
BCR
5 4
ABW4 ABW3
1 1
R/W R/W R/W
0 0
R/W R/W R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
3 2 1
ABW2 ABW1
1 1 1
R/W R/W
0 0 0
R/W R/W
Initial Value
2
H'FF*
H'FF
H'FF
H'FF
3
H'FE*
H'0F
H'FF
H'C6
0
ABW0
1
R/W
0
R/W
to
15