Interrupts lost while interrupts are disabled

[dk2]

Posted on October 30, 2009 at 04:14

Interrupts lost while interrupts are disabled

[dk2]

Posted on May 17, 2011 at 13:28

Hi,

in my program, the Systick-interrupt sets an external

interrupt request in the EXTI-SWIER. When this is done, while the

corresponding bit in the EXTI-IMR is set, everything is ok.

But when:

- the main routine disables this int by clearing the IMR-bit

- with the cleared IMR-bit the SWIER-bit is set (by the still enabled

Systick-int with high priority)

- the main routine reenables the int

then the SWIER bit remains set, but no pending request is set and no int

is generated.

It looks like the SWIER is ANDED with the IMR, in contrast to the

block diagram in RM0008 (June 2009-Version), 9.2.2- Figure 20.

But even then there should be an interrupt when SWIER and IMR - bits

are set, regardless of the sequence of their settings. Right?

Even more, it is said that the PendingRequestRegister must be cleard by

software by writing a 1 to the bit. But this is done by hardware at the

start of the interrupt service routine. At the same time the SWIER-Bit

is automatically cleared. So, no action has to be taken in software.

(That's what I found out).

Detlef