376 datasheet(17/95 Pages) INTEL

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376 EMBEDDED PROCESSOR

Table 25 Interrupt Vector Assignments

Instruction Which

Return Address

Function

Interrupt

Can Cause

Points to

Type

Number

Exception

Faulting

Instruction

Divide Error

DIV IDIV

Yes

FAULT

Debug Exception

Any Instruction

Yes

TRAP

NMI Interrupt

INT 2 or NMI

NMI

One-Byte Interrupt

INT

TRAP

Interrupt on Overflow

INTO

TRAP

Array Bounds Check

BOUND

Yes

FAULT

Invalid OP-Code

Any Illegal Instruction

Yes

FAULT

Device Not Available

ESC WAIT

Yes

FAULT

Double Fault

Any Instruction That Can

ABORT

Generate an Exception

Coprocessor Segment Overrun

ESC

ABORT

Invalid TSS

JMP CALL IRET INT

Yes

FAULT

Segment Not Present

Segment Register Instructions

Yes

FAULT

Stack Fault

Stack References

Yes

FAULT

General Protection Fault

Any Memory Reference

Yes

FAULT

Intel Reserved

14 – 15

Coprocessor Error

ESC WAIT

Yes

FAULT

Intel Reserved

17 – 32

Two-Byte Interrupt

0 – 255

INT n

TRAP

Some debug exceptions may report both traps on the previous instruction and faults on the next instruction

Interrupts through Interrupt Gates automatically re-

set IF disabling INTR requests Interrupts through

Trap Gates leave the state of the IF bit unchanged

Interrupts through a Task Gate change the IF bit ac-

cording to the image of the EFLAGs register in the

task’s Task State Segment (TSS) When an IRET

instruction is executed the original state of the IF bit

is restored

Non-Maskable Interrupt

Non-maskable interrupts provide a method of servic-

ing very high priority interrupts When the NMI input

is pulled HIGH it causes an interrupt with an internal-

ly supplied vector value of 2 Unlike a normal hard-

ware interrupt no interrupt acknowledgement se-

quence is performed for an NMI

While executing the NMI servicing procedure the

80376 will not service any further NMI request or

INT requests until an interrupt return (IRET) instruc-

tion is executed or the processor is reset If NMI

occurs while currently servicing an NMI its presence

will be saved for servicing after executing the first

IRET instruction The disabling of INTR requests de-

pends on the gate in IDT location 2

Software Interrupts

A third type of interruptexception for the 80376 is

the software interrupt An INT n instruction causes

the processor to execute the interrupt service rou-

tine pointed to by the nth vector in the interrupt table

A special case of the two byte software interrupt

INT n is the one byte INT 3 or breakpoint interrupt

By inserting this one byte instruction in a program

the user can set breakpoints in his program as a

debugging tool

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