BRCR—Bus Release Control Register
H'F3
Bus controller
ISCR—IRQ Sense Control Register
H'F4
Interrupt controller
IER—IRQ Enable Register
H'F5
Interrupt controller
Bit
Modes
1, 2,
5, 7
Initial value
Read/Write
Initial value
Read/Write
Modes
3, 4, 6
7
A23E
1
—
1
R/W
6
A22E
1
—
1
R/W
5
A21E
1
—
1
R/W
3
—
1
—
1
—
2
—
1
—
1
—
1
—
1
—
1
—
0
BRLE
0
R/W
0
R/W
4
—
1
—
1
—
Bus release enable
Address 23 to 21 enable
0
The bus cannot be released to an external device
1
The bus can be released to an external device
0
Address output
1
Other input/output
Bit
Initial value
Read/Write
7
—
0
R/W
6
—
0
R/W
5
IRQ5SC
0
R/W
4
IRQ4SC
0
R/W
3
IRQ3SC
0
R/W
2
IRQ2SC
0
R/W
1
IRQ1SC
0
R/W
0
IRQ0SC
0
R/W
IRQ to IRQ sense control
0
Interrupts are requested when IRQ to IRQ inputs are low
1
Interrupts are requested by falling-edge input at IRQ to IRQ
5
0
5
5
0
0
Bit
Initial value
Read/Write
7
—
0
R/(W)
6
—
0
R/(W)
5
IRQ5E
0
R/(W)
4
IRQ4E
0
R/(W)
3
IRQ3E
0
R/(W)
2
IRQ2E
0
R/(W)
1
IRQ1E
0
R/(W)
0
IRQ0E
0
R/(W)
IRQ to IRQ enable
0
IRQ to IRQ interrupts are disabled
1
IRQ to IRQ interrupts are enabled
5
0
5
5
0
0
821
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