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CHAPTER 7 External Interrupt 1 Circuit
MB89960 series
7.4 External Interrupt 1 Circuit
Interrupts
The external interrupt circuit can generate interrupt requests when it detects a
specified edge on the signal input to an external interrupt pin.
s Interrupts When the External Interrupt Circuit is Operating
On detecting a specified edge on an external interrupt input, the external interrupt circuit sets
the corresponding external interrupt request flag bit (EIC1, EIC2: EIR0 - EIR2) to “1”. An
interrupt request to the CPU (IRQ0 - IRQ2) is generated at this time if the corresponding
interrupt request enable bit is enabled (EIC1, EIC2: EIE0 - EIE2 = “1”). Always write “0” to the
corresponding external interrupt request flag bit in the interrupt processing routine to clear the
interrupt request.
Caution: When enabling interrupts (EIE0 - EIE2 = “1”) after exit of a reset, always clear the
corresponding external interrupt request flag bit (EIR0 - EIR2 = “0”) at the same time.
Interrupt processing cannot return if the external interrupt request flag bit is “1” and the
interrupt request enable bit is enabled. Always clear the external interrupt request flag
bit.
Notes:Cancelling stop mode using an interrupt is only possible using the external interrupt
circuit.
An interrupt request is generated immediately if the external interrupt request flag bit is
“1” when the interrupt request enable bit is changed from disabled to enabled (“0”
→
“1”).
s Register and Vector Table for the External Interrupt Circuit Interrupts
Reference: See “3.4.2 Interrupt Processing” for details on the operation of interrupts.
s Notes when changing edge polarity selection
When changing the edge polarity for INT10, INT11 or INT12, always write “0” into the
corresponding EIR bits. That will prevent accidentially creating an interrrupt.
Table 7.4
Register and Vector Table for the External Interrupt Circuit Interrupts
Interrupt
Interrupt Level Setting Register
Vector Table Address
Register
Setting Bits
Upper
Lower
IRQ0
ILR1 (007CH)
L01 (bit1)
L00 (bit0)
FFFAH
FFFBH
IRQ1
L11 (bit3)
L10 (bit2)
FFF8H
FFF9H
IRQ2
L21 (bit5)
L20 (bit4)
FFF6H
FFF7H