Global Interruption Disable/Enable

There are really two solutions to this problem.

1. If you need just a single routine that has the interrupt system disabled, you should write a __swi function. swi (= software interrupt) prevents that a function can be interrupted by an __irq. __fiq functions are not blocked.

2. For specific interrupt blocking see:
http://www.keil.com/support/docs/2888.htm

Reinhard

As I understand, if program uses both IRQ and FIQ, the __swi function cannot be used. More, if I want to disable interruptions not for the whole function, but only for a part of code, I must write to the VICIntEnClr register as in the example. But in the example one need to disable only TIMER0 interruption. What if I need to disable all interruptions?
If I write

temp = VICIntEnable;
VICIntEnClr = temp;
...
VICIntEnable = temp;

there is a risk, that if interruption happened between the two first operators, and the interrupt handler changes the value of the VICIntEnable register, a wrong value will be restored by the last operator.
Am I wrong?
Is there an absolutely reliable way to disable ALL interruptions for LPC2100? It is so easy in other microcontrollers.

Varuzhan

You are correct about the __swi, but why do you need to block an fiq?

It would be dangerous to change VICIntEnable in an interrupt function! You should not partice this programming style.

Reinhard

As I understand, if program uses both IRQ and FIQ, the __swi function cannot be used. More, if I want to disable interruptions not for the whole function, but only for a part of code, I must write to the VICIntEnClr register as in the example. But in the example one need to disable only TIMER0 interruption. What if I need to disable all interruptions?
If I write

temp = VICIntEnable;
VICIntEnClr = temp;
...
VICIntEnable = temp;

there is a risk, that if interruption happened between the two first operators, and the interrupt handler changes the value of the VICIntEnable register, a wrong value will be restored by the last operator.
Am I wrong?
Is there an absolutely reliable way to disable ALL interruptions for LPC2100? It is so easy in other microcontrollers.

Varuzhan

I am sorry for repeating message - bad working telephone line.
I agree about the bad stile.
Then can I define two macros:

unsigned int temp;
#define _DISABLE (temp = VICIntEnable; VICIntEnClr = temp);

#define _ENABLE (VICIntEnable = temp;)

and use them in my code?

Thank you,
Varuzhan

Sure, without brackets

Each ARM controller is somehow different.

A generic solution to disable all interrupts is to set the CPSR I + F flag (similar code as documented under: http://www.keil.com/support/docs/2910.htm).

But tell my: why can you not use the __swi method?

Reinhard

Thank you very much!
The __swi method is really nice, but sometimes one will not want to have a function call overhead to protect only a couple of instructions.

Another question: do the methods, mentioned in whole this topik, including the __swi, protect from Spurious Interrupts?

Varuzhan

The __swi method is really nice, but sometimes one will not want to have a function call overhead to protect only a couple of instructions.

Isn't the __swi call less code (and overhead) than disabling interrupts?

do the methods, mentioned in whole this topik, including the __swi, protect from Spurious Interrupts?

Masking interrupts inhibits interrupts (spurious or not). However, a spurious interrupt is an unexpected interrupt. Once interrupts are unmasked, the spurious interrupt triggers. Then, the interrupt handler will need to handle it.

Jon