4.3.2 Interrupt-Related Registers
The interrupt-related registers are the system control register (SYSCR), IRQ sense control register
(ISCR), and IRQ enable register (IER).
Table 4-3. Registers Read by Interrupt Controller
Name
Abbreviation
Read/Write
Address
System control register
SYSCR
R/W
H'FFC4
IRQ sense control register
ISCR
R/W
H'FFC6
IRQ enable register
IER
R/W
H'FFC7
System Control Register (SYSCR)—H'FFC4
Bit
7
6
5
4
3
2
1
0
SSBY
STS2
STS1
STS0
—
NMIEG
—
RAME
Initial value
0
0
0
0
1
0
1
1
Read/Write
R/W
R/W
R/W
R/W
—
R/W
—
R/W
The valid edge on the NMI line is controlled by bit 2 (NMIEG) in the system control register.
Bit 2—NMI Edge (NMIEG): Determines whether a nonmaskable interrupt is generated on the
falling or rising edge of the NMI input signal.
Bit 2
NMIEG
Description
0
An interrupt is generated on the falling edge of NMI.
(Initial state)
1
An interrupt is generated on the rising edge of NMI.
See section 2.2, “System Control Register,” for information on the other SYSCR bits.
IRQ Sense Control Register (ISCR)—H'FFC6
Bit
7
6
5
4
3
2
1
0
—
—
—
—
—
IRQ
2
SC IRQ
1
SC IRQ
0
SC
Initial value
1
1
1
1
1
0
0
0
Read/Write
—
—
—
—
—
R/W
R/W
R/W
Bits 3 to 7—Reserved: These bits cannot be modified and are always read as “1.”
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Summary of Contents for H8/326 Series
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