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RM0016

Interrupt controller (ITC)

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.

When an interrupt request is not serviced immediately, it is latched and then processed

when its software priority combined with the hardware priority becomes the highest one.

Note:

The hardware priority is exclusive while the software one is not. This allows the previous

process to succeed with only one interrupt.

RESET, TLI and TRAP are considered as having the highest software priority in the decision

process.

See Figure 14 for a description of pending interrupt servicing process.

Figure 14. Priority decision process

6.2.2

Interrupt sources

Two interrupt source types are managed by the STM8 interrupt controller:

•

Non-maskable interrupts: RESET, TLI and TRAP

•

Maskable interrupts: external interrupts or interrupts issued by internal peripherals

Non-maskable interrupt sources

Non-maskable interrupt sources are processed regardless of the state of bits I1 and I0 of the

CCR register (see Figure 13). PC, X, Y, A and CCR registers are stacked only when a TRAP

MSv45261V1

SOFTWARE

PRIORITY

PENDING

INTERRUPTS

HIGHEST SOFTWARE

PRIORITY SERVICED

HIGHEST HARDWARE

PRIORITY SERVICED

Different

Same

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