HC705RC16GRSSLASHD datasheet(36/120 Pages) NXP

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Interrupts

General Release Specification

MC68HC705RC16 — Rev. 3.0

Interrupts

4.3 CPU Interrupt Processor

Interrupts cause the processor to save register contents on the stack

and to set the interrupt mask (I bit) to prevent additional interrupts. Unlike

reset, hardware interrupts do not cause the current instruction execution

to be halted, but are considered pending until the current instruction is

complete.

If interrupts are not masked (I bit in the CCR is clear) and the

corresponding interrupt enable bit is set, the processor will proceed with

interrupt processing. Otherwise, the next instruction is fetched and

executed. If an interrupt occurs, the processor completes the current

instruction, stacks the current CPU register state, sets the I bit to inhibit

further interrupts, and finally checks the pending hardware interrupts. If

more than one interrupt is pending after the stacking operation, the

interrupt with the highest vector location shown in Table 4-1 will be

serviced first. The SWI is executed the same as any other instruction,

regardless of the I-bit state.

When an interrupt is to be processed, the CPU fetches the address of

the appropriate interrupt software service routine from the vector table at

locations $3FF6–$3FFF as defined in Table 4-1.

Table 4-1. Vector Address for Interrupts and Reset

Flag Name

Interrupt

CPU

Interrupt

Vector Address

N/A

Reset

RESET

$3FFE–$3FFF

N/A

Software Interrupt

SWI

$3FFC–$3FFD

N/A

External Interrupts*

IRQ

$3FFA–$3FFB

MCSR

EOC

End of Cycle

Interrupt

CMT

$3FF8–$3FF9

CTCSR

CTOF,

RTIF

Real-Time Interrupt

Core Timer

Overﬂow

CORE

TIMER

$3FF6–$3FF7

*External interrupts include IRQ and port B keyscan sources.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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