STR720 datasheet(34/401 Pages) STMICROELECTRONICS

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STR720 - ARCHITECTURE OVERVIEW

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Figure 4. IRQ Interrupt Vectorization

This mechanism allows a jump to virtually any location of the 4GB memory space. However,

since the channel dependent portion of IVR are the lower 16 bits, once the base address (in

the upper part) has been fixed the interrupt handler routines can only be within a 64Kbyte

range from that base address.

5.2 Wake-up/Interrupt management Unit (WIU)

The Wake-up/Interrupt Management Unit can be seen as an extension of the number of

external interrupt lines but it can also manage up to 16 wake-up lines capable of exiting STOP

mode:

■

4 external wake-up lines all connected to the IRQ0 channel of the interrupt controller. These

wake-up lines have dedicated input ports.

■

1 external wake-up line directly mapped to a dedicated channel of the interrupt controller

(IRQ1). This wake-up line has a dedicated input port.

■

10 internal wake-up lines connected to the IRQ2 channel of the interrupt controller module.

The ‘internal” lines are mapped on some significant STR720 signals.

The external wake-up pins (available as alternate function of general purpose I/O lines) can

be programmed as plain external interrupt lines or as wake-up lines to exit STOP mode. When

the external lines are defined as wake-up pins a programmable signal edge will

asynchronously trigger the wake-up event, changing the status of the alternate output function

STOP_REQ, associated to P3.7 and allowing the external power control to restore system

main clock source. In this way STOP mode can be exited without resetting the whole system,

provided that STOP_REQ is enabled.

0x0001 8000

IVR = 0x0001 8000

EIC IVR stores the absolute address of the

0xFFFF FC18

INTERRUPT

SERVICE

ROUTINE

LDR PC, [PC, offset]

0x0000 0018

offset = 0xFFFF FC18 - 0x20

= 0xFFFF FBF8

First instruction of the ISR is located

at address 0x0001 8000

IRQ

USER

CODE

PC <= [PC, offset]

Interrupt Service Routine

PC = 0x0000 0020

PC = 0x0001 8000

PC = 0xFFFF FC18

Interrupt request

Jump at address 0x0000 0018h:

IVR used by previous instruction as base address

execution of the instruction which loads PC with

EIC IVR address 0xFFFF FC18h

for the particular interrupt service routine

Starting of execution of interrupt service routine

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