Posted on September 21, 2012 at 18:08The ST32F4xx user manual, RM0090, on page 205, for the EXTI_PR (pending register) bits says:
> This bit is cleared by writing a 1 to the bit
> or by changing the sensitivity of the edge detector.
The latter one does not appear to be true - changing the corresponding bit in either the EXTI_RTSR or EXTI_FTSR register does not have influence on the state of EXTI_PR register.
A simple test routine below - should end with EXTI_PR in 0, but on the eval board I have at hand it ends with EXTI_PR == 1.
While strictly speaking this is not a bug and it's trivial to work around (simply using the first method); it is at least a documentation error.
Could anybody please confirm or reject?
Thanks,
Jan Waclawek
EXTI->RTSR = 0; // both edge detector setting registers set to 0
EXTI->FTSR = 0; // (they are 0 by default, but just to be sure)
EXTI->IMR = 1; // unmask interrupt for 0th bit
EXTI->SWIER = 1; // this forces the _PR register to 1
__asm(''nop''); // here check that _PR is indeed 1
EXTI->SWIER = 0; // shouldn't really be needed
// changing the edge detector should clear the pending _PR bit
// we can try changing either rising or falling
EXTI->RTSR = 1;
// EXTI->FTSR = 1;
__asm(''nop''); // okay so here _PR should be 0 again
#exti
