Misunderstanding in the RM0008 manual for STM32F103 at P212

[Klavs Rommedahl]

Posted on April 17, 2018 at 13:18

Hello.

  At page 212 in the manual RM0008 for the STM32F103 device, some part of the internal/software event is explained. Under the EXTI_PR it states, this bit is cleared by writing a '1'into the bit. But just above it says 1 = trigger occurred = bit is set ??? I am confused.

  I do follow the part of setting up pins and level detections, but set/reset part of SWIER and PR confuses a bit

:)

 ???

BRGDs

  Klavs.

[waclawek.jan]

Posted on April 17, 2018 at 18:42

Hardware sets the EXTI_PR bits so that you can read 1 out from them.

By software, the bits you write 1 into them get cleared, so you can read 0 out of them.

Think of 20 R-S flip-flops; with the S line of each flip-flop tied to the internal hardware detecting the edge; the R line tied to outputs 0..19 of a multibit gate which opens from the common bus when the address decoder detects write to the register's address; and the outputs of latches connected to inputs of the gate opening to the common bus when the address decoder detects read from the register's address.

JW

[Klavs Rommedahl]

Posted on April 18, 2018 at 08:41

Just to confirm, but like this ?

[waclawek.jan]

Posted on April 18, 2018 at 09:30

Yes, with a few minor corrections:

JW

[Klavs Rommedahl]

Posted on April 18, 2018 at 09:55

Thank You That drawing is 4.000.000.000 times easier to understand than the text in RM0008

:)

.