68HC05CT4 datasheet(39/142 Pages) FREESCALE

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Interrupts

Hardware Interrupts

MC68HC05CT4 — Rev. 2.0

General Release Specification

Interrupts

4.6 Hardware Interrupts

All hardware interrupts except RESET are maskable by the I bit in the

CCR. If the I bit is set, all hardware interrupts (internal and external) are

disabled. Clearing the I bit enables the hardware interrupts. The two

types of hardware interrupts are explained in the following sections.

4.7 External Interrupt (IRQ)

The IRQ pin provides an asynchronous interrupt to the CPU. A block

diagram of the IRQ function is shown in Figure 4-2.

NOTE:

The BIH and BIL instructions will apply only to the level on the IRQ pin

itself, and not to the output of the logic OR function with the port C IRQ

interrupts. The state of the individual port C pins can be checked by

reading the appropriate port C pins as inputs.

Figure 4-2. IRQ Function Block Diagram

The IRQ pin is one source of an external interrupt. All port C pins

(PC0–PC7) act as other external interrupt sources if the keyscan feature

is enabled as specified by the user.

When edge sensitivity is selected for the IRQ interrupt, it is sensitive to:

•

Falling edge on the IRQ pin

•

Falling edge on any port C pin with keyscan enabled

IRQ

LATCH

IRQ PIN

LEVEL

(MASK OPTION)

TO IRQ

PROCESSING

IN CPU

PORT C

TO BIH & BIL

INSTRUCTION

SENSING

RST

IRQ VECTOR FETCH

VDD

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