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ST90T158 Fiches technique(PDF) 54 Page - STMicroelectronics |
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ST90T158 Fiches technique(HTML) 54 Page - STMicroelectronics |
54 / 190 page 54/190 ST90158 - INTERRUPTS ARBITRATION MODES (Cont’d) End of Interrupt Routine The iret Interrupt Return instruction executes the following steps: – The Flag register is popped from system stack. – If ENCSR is set, CSR is popped from system stack. – The PC high byte is popped from system stack. – The PC low byte is popped from system stack. – All unmasked Interrupts are enabled by setting the CICR.IEN bit. – The priority level of the interrupted routine is popped from the special register (NICR) and copied into CPL. – If ENCSR is reset, CSR is used instead of ISR, unless the program returns to another nested routine. The suspended routine thus resumes at the inter- rupted instruction. Figure 23 contains a simple example, showing that if the ei instruction is not used in the interrupt service routines, nested and concurrent modes are equivalent. Figure 24 contains a more complex example showing how nested mode allows nested interrupt processing (enabled inside the interrupt service routinesi using the ei instruction) according to their priority level. Figure 24. Complex Example of a Sequence of Interrupt Requests with: - Nested mode - IEN set to 1 during the interrupt routine execution INT 2 INT 3 CPL=3 INT 0 CPL=0 INT6 6 5 4 3 2 1 0 7 MAIN INT 5 INT 4 INT0 INT4 INT3 INT2 CPL is set to 7 CPL=5 CPL=4 CPL=2 CPL=7 ei INTERRUPT 2 HAS PRIORI TY LEVEL 2 INTERRUPT 3 HAS PRIORI TY LEVEL 3 INTERRUPT 4 HAS PRIORI TY LEVEL 4 INTERRUPT 5 HAS PRIORI TY LEVEL 5 INT 2 INT 4 CPL=2 CPL=4 INT 5 CPL=5 MAIN ei ei INT 2 CPL=2 INT 6 CPL=6 INT5 INT2 ei INTERRUPT 6 HAS PRIORI TY LEVEL 6 INTERRUPT 0 HAS PRIORI TY LEVEL 0 CPL6 > CPL3: INT6 pending CPL2 < CPL4: Serviced just after ei Priority Level of Interrupt Request ei 9 |
Numéro de pièce similaire - ST90T158 |
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Description similaire - ST90T158 |
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