ST72324BJ2 datasheet(37/188 Pages) STMICROELECTRONICS

Part #	ST72324BJ2

Description	8-bit MCU, 3.8 to 5.5 V operating range with 8 to 32 Kbyte Flash/ROM, 10-bit ADC, 4 timers, SPI, SCI

PDF	188 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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ST72324B

Interrupts

37/188

Figure 18.

Interrupt processing flowchart

7.2.1

Servicing pending interrupts

As several interrupts can be pending at the same time, the interrupt to be taken into account

is determined by the following two-step process:

●

the highest software priority interrupt is serviced,

●

if several interrupts have the same software priority then the interrupt with the highest

hardware priority is serviced first.

Figure 19 describes this decision process.

Figure 19.

Priority decision process flowchart

Table 13.

Interrupt software priority levels

Interrupt software priority

Level

Level 0 (main)

Low

High

Level 1

Level 2

Level 3 (= interrupt disable)

“IRET”

RESTORE PC, X, A, CC

Stack PC, X, A, CC

load I1:0 from interrupt SW reg.

Fetch next

Reset

TRAP

Pending

nstruction

I1:0

from stack

load PC from interrupt vector

Interrupt has the same or a

lower software priority

The interrupt

stays pending

than current one

Execute

instruction

nterrupt

PENDING

SOFTWARE

Different

INTERRUPTS

Same

HIGHEST HARDWARE

PRIORITY SERVICED

PRIORITY

HIGHEST SOFTWARE

PRIORITY SERVICED

ST72324BJ2 Datasheet(PDF) 37 Page - STMicroelectronics

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