
Interrupts ST72321xx-Auto
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flag is set in the peripheral status registers and if the corresponding enable bit is set in
the peripheral control register.
The general sequence for clearing an interrupt is based on an access to the status
register followed by a read or write to an associated register.
Note: The clearing sequence resets the internal latch. A pending interrupt (that is, waiting to be
serviced) will therefore be lost if the clear sequence is executed.
7.3 Interrupts and low power modes
All interrupts allow the processor to exit the Wait low power mode. On the contrary, only
external and other specified interrupts allow the processor to exit from the Halt modes (see
column “Exit from Halt/Active Halt” in Table 20: Interrupt mapping). When several pending
interrupts are present while exiting Halt mode, the first one serviced can only be an interrupt
with “exit from Halt mode” capability and it is selected through the same decision process
shown in Figure 18.
Note: If an interrupt that is not able to exit from Halt mode is pending with the highest priority when
exiting Halt mode, this interrupt is serviced after the first one serviced.
7.4 Concurrent and nested management
The following Figure 19 and Figure 20 show two different interrupt management modes. The
first is called concurrent mode and does not allow an interrupt to be interrupted, unlike the
nested mode in Figure 20. The interrupt hardware priority is given in this order from the
lowest to the highest: MAIN, IT4, IT3, IT2, IT1, IT0, TLI. The software priority is given for
each interrupt.
Warning: A stack overflow may occur without notifying the software of
the failure.
Figure 19. Concurrent interrupt management
MAIN
IT4
IT2
IT1
TRAP
IT1
MAIN
IT0
I1
HARDWARE PRIORITY
SOFTWARE
3
3
3
3
3
3/0
3
11
11
11
11
11
11 / 10
11
RIM
IT2
IT1
IT4
TRAP
IT3
IT0
IT3
I0
10
PRIORITY
LEVEL
USED STACK = 10 BYTES
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