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Klavs Rommedahl
Klavs Rommedahl
Associate II
April 17, 2018
Question

Misunderstanding in the RM0008 manual for STM32F103 at P212

  • April 17, 2018
  • 1 reply
  • 1460 views
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.

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    1 reply

    waclawek.jan
    waclawek.jan
    Super User
    April 17, 2018
    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
    Klavs RommedahlAuthor
    Associate II
    April 18, 2018
    Posted on April 18, 2018 at 08:41

    Just to confirm, but like this ?0690X00000604aHQAQ.jpg

    waclawek.jan
    waclawek.jan
    Super User
    April 18, 2018
    Posted on April 18, 2018 at 09:30

    Yes, with a few minor corrections:

    0690X0000060AdlQAE.png

    JW

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