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GPIO Speed setting Fast/High (50/100MHz) - IO Compensation cell

Question asked by bil.til on Jan 27, 2012
Latest reply on Jan 28, 2012 by bil.til
Hi,
in the reference manual RM0090 for STMF4, in chapter 7.1 it is recommended to activate the "IO compensation cell" (Register SYSCFG_CMPCR), if outputs are used with speed settings of 50 or 100 MHz (GPIOx_OSPEEDR-Register).

If I search for "SYSCFG_CMPCR" in the folder STM32F2xx_StdPeriph_Lib_V1.0.0\Libraries, then I get a hit in the file stm32f2xx_syscfg.c, there is a function named "SYSCFG_CompensationCellCmd", and in the release notes, they specify that this command was added in April 2011 only. But if I search the source folder for the usage of this command, it is never used.

Anyone who has experience with the influence of this "IO compensation cell"? Is it really a good a advise to use it?

Further: In the reference manual 6.4.3, description of register GPIOx_SPEEDR, it says for hi-speed setting: 100 MHz High Speed on 30pF (80 MHz Output max speed on 15pF). Is this real or maybe some misprint? (for higher capacitive pin load I definitely would expect some lower speed ...). (??)

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