EM6812F2TP24B datasheet(70/81 Pages) EMMICRO

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EM6812

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14.3.4 Processor vector table

Address 1,2 and 3 of the program memory are reserved for interrupt subroutine calls. Generally the first four addresses of

the program memory are reserved for the processor vector table. The address 0 of the program memory contains the jump

to the start-up routine

Table 61. Processor vector table

Address

Accessed by

Description

Priority

ResCPU

Any reset, start-up address

Maximal, above interrupts

IN1

Interrupt level 1

medium

IN2

Interrupt level 2

low

IN3

Interrupt level 0

high

14.3.5 Context Saving

Since an interrupt may occur any time during normal program execution, there is no way to know which processor registers

are used by the user program. For this reason, all resources modified in the interrupt service routine have to be saved upon

entering and restored when leaving the service routine. The flags(C,V) and the accumulator (A) must always be saved,

since most instructions will modify them. Other registers need only to be saved when they are modified in the interrupt

service routine. There is a particular way to follow when saving resources. The accumulator should be saved first, followed

by the flags and then the other registers

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