ST72F324BJ STMICROELECTRONICS [STMicroelectronics], ST72F324BJ Datasheet - Page 37

• Manufacturer Part Number: ST72F324BJ
• 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
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST72324B
7.2.1
Table 13.
Figure 18. Interrupt processing flowchart
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:
●
●
Figure 19
Figure 19. Priority decision process flowchart
Level 0 (main)
Level 1
Level 2
Level 3 (= interrupt disable)
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.
describes this decision process.
RESTORE PC, X, A, CC
Interrupt software priority
Interrupt software priority levels
Reset
from stack
HIGHEST HARDWARE
PRIORITY SERVICED
Same
Y
instruction
Pending
I
Fetch next
nterrupt
I
nstruction
Execute
N
“IRET”
N
INTERRUPTS
SOFTWARE
PRIORITY
PENDING
HIGHEST SOFTWARE
PRIORITY SERVICED
Y
stays pending
The interrupt
Interrupt has the same or a
Level
Different
High
Low
lower software priority
load I1:0 from interrupt SW reg.
than current one
load PC from interrupt vector
Stack PC, X, A, CC
I1
1
1
0
0
TRAP
I1:0
N
Y
Interrupts
I0
0
1
0
1
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