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Chapter 3    Interrupts

III - 50

External Interrupts

If there is at least one input signal, from the P60 to P63 pins, shows low level, the external interrupt

4 is generated at the falling edge.

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Key Input Interrupt Setup Example (External interrupt 4)

After P60 to P63 of port 6 are set to key input pins and key is input (low level), the external interrupt 4 (IRQ4)

is generated. An example setup procedure, with a description of each step is shown below.

(1)

Set the P6DIR3-0 flag of the port 6 direction

control register (P6DIR) to "0000" to set P60 to

P63 pins to input pins.

(2)

Set the P6PLU 3-0 flag of the port 6 pull-up

resistance control register (P6PLU) to"1111"

to add the pull-up resistance to P60 to

P63 pins.

(3)

Set the IRQ4SEL flag of the port 6 key interrupt

control register (P6IMD) to "1" to select the

external interrupt 4 source to the port 6 key

interrupt.

(4)

Set the P6KYEN 2-1 flag of the port 6 key

interrupt control register (P6IMD) to "11" to

set P60 to P63 pins to key input pins.

(5)

Set the interrupt level by the IRQ4LV1-0 flag

of the IRQ4ICR register.

If the interrupt request flag has been already

set, clear the it.

[            Chapter 3  3-1-4. Interrupt flag setup  ]

(6)

Set the IRQ4IE flag of the IRQ4ICR register

to "1" to enable the interrupt.

Setup Procedure

(1)

Set the key input pin to input.

P6DIR (x'3F36')

bp3-0

: P6DIR3-0

= 0000

(2)

Set the pull-up resistance.

P6PLU (x'3F46')

bp3-0

: P6PLU3-0 = 1111

(3)

Select the key input interrupt.

P6IMD (x'3F3E')

bp7

: IRQ4SEL = 1

(4)

Select the key input pin.

P6IMD (x'3F3E')

bp1-0

: P6KYEN2-1= 11

(5)

Set the interrupt level.

IRQ4ICR (x'3FE6')

bp7-6

: IRQ4LV1-0= 10

(6)

Enable the interrupt.

IRQ4ICR (x'3FE6')

bp1

: IRQ4IE

= 1

Description

Note : The above (3) and (4) are set at the same time.

The setup of the key input should be done before the interrupt is enabled.