Bits 0 to 2—IRQ
0
to IRQ
2
Sense Control (IRQ
0
SC to IRQ
2
SC): These bits determine whether
IRQ
0
to IRQ
2
are level-sensed or sensed on the falling edge.
Bits 0 to 2
IRQ
0
SC to IRQ
2
SC
Description
0
An interrupt is generated when IRQ
0
to IRQ
2
(Initial state)
inputs are Low.
1
An interrupt is generated by the falling edge of the IRQ
0
to IRQ
2
inputs.
IRQ Enable Register (IER)—H'FFC7
Bit
7
6
5
4
3
2
1
0
—
—
—
—
—
IRQ
2
E
IRQ
1
E
IRQ
0
E
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.”
Bits 0 to 2—IRQ
0
to IRQ
2
Enable (IRQ
0
E to IRQ
2
E): These bits enable or disable the IRQ
0
to
IRQ
2
interrupts individually.
Bits 0 to 2
IRQ
0
E to IRQ
2
E
Description
0
IRQ
0
to IRQ
2
interrupt requests are disabled.
(Initial state)
1
IRQ
0
to IRQ
2
interrupt requests are enabled.
When edge sensing is selected (by setting bits IRQ
0
SC to IRQ
7
SC to “1”), it is possible for an
interrupt-handling routine to be executed even though the corresponding enable bit (IRQ
0
E to
IRQ
7
E) is cleared to “0” and the interrupt is disabled. If an interrupt is requested while the
enable bit (IRQ
0
E to IRQ
7
E) is set to “1,” the request will be held pending until served. If the
enable bit is cleared to “0” while the request is still pending, the request will remain pending,
although new requests will not be recognized. If the interrupt mask bit (I) in the CCR is
cleared to “0,” the interrupt-handling routine can be executed even though the enable bit is
now “0.”
65
Summary of Contents for H8/326 Series
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