Hi Dana,
On 31.05.2018 09:01, Dana Myers wrote: > On 5/30/2018 11:41 PM, Steve wrote: >> It just dawned on me, that the stm32 normally executes its programs >> out of flash. >> >> I was thinking the flash stored the software, and the first thing it >> did, was move the code to ram for execution. I was thinking the flash >> access time was too slow. > > It depends on the specific STM32 part you have. STM32F4-series parts have > 128-bit wide flash that effectively runs at 0-wait. I haven't verified > the > bigger STM32F7-series but would be surprised if this wasn't also the > case there. > The STM32F4 needs 6 or 7 wait states configuration for random flash access if running at 168/180 Mhz top speed according to my memory. Since the processor fetches 4 32 bit values at time from flash, for linear access it is not as bad most of the time but still slower than RAM. Reducing flash data access was one of the tricks I used to speed up the codec2 code so that we could run it as part of the UHSDR firmware on STM32F4 (the UHSDR has to run full SDR TRX DSP as opposed to the SM1000 which just does audio processing part). > Some of the smaller STM32F3-series parts have 'CCM' RAM which can > be executed from, but it's a bit of a hassle to set up. > Also the STM32F4 has 64k of CCM RAM, which can be used to run some highspeed code (or data but no DMA there). The various STM32 devices have different memories with funny names like ITCM, CCM, DTCM, ... all of these have special properties (faster for code, for data, not disturbable by DMA, ... ). 73 Danilo > Cheers, > Dana K6JQ > > > ------------------------------------------------------------------------------ > > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Freetel-codec2 mailing list > Freetel-codec2@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
