STM32F413VG FSMC Muxed or Non-Muxed?

thinkit z · ‎2017-02-22

Posted on February 22, 2017 at 10:52

I want to control several FPGA registers by FSMC bus. It's about 30 registers in the FPGA, each register 16bits.

MCU package is LQFP100. STM32CubeMX makes the FSMC bus 3 options: LCD ; Muxed NOR Flash; Muxed PSRAM (fig 1). so Muxed PSRAM is the right choice. In the Muxed mode, the data and address bus is FSMC_DA0, FSMC_DA1,...FSMC_DA15.(fig 2)

BUT, In the datasheet , the chip has standalone DATA bus FSMC_D0..FSMC_D1..FSMC_D2....FSMC_D15 (fig 2) and standalone ADDRESS bus FSMC_A0, FSMC_A16, FSMC_A17..FSMC_A23(fig 3). The address bus is 9 bit, it is enough for 30+ registers. Can I used FSMC in non-Muxed mode for this application? If non-muxed mode is ok, I will save register-to-fpga-out time and fpga layout.

Thanks!

fig 1

fig 2

fig 3

#muxed-non-muxed* #fsmc #stm32f413vg

waclawek.jan · ‎2017-02-22

Posted on February 22, 2017 at 12:58

Most probably you can (I am not ST so this is not a hard guarantee), if you don't need a continuous address space. I am using an STM32F407VG in this fashion.

JW

Amel NASRI · ‎2017-02-22

Posted on February 22, 2017 at 17:29

Hi,

As stated in the note (1) of table 2 in

http://www.st.com/content/ccc/resource/technical/document/datasheet/group3/f6/1d/4a/d9/f9/96/43/2a/DM00282249/files/DM00282249.pdf/jcr:content/translations/en.DM00282249.pdf

, only muxed mode is supported for 100-pin packages: '

100 pins packages: only 1 external memory of up to 16 MB in multiplexed mode.

'.

-Amel

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waclawek.jan · ‎2017-02-22

Posted on February 22, 2017 at 18:04

Amel,

I believe this is simply a misinterpretation of a not-that-well-formulated note. I don't believe there is anything which would prevent non-muxed modes in the 100 pin package; this would be very weird.

IMO that note is there just to avoid disappointment from people who don't read the rest of the DS thus don't realize that the low address pins are not present in that package. Thus, the non-muxed mode *is* usable, but only for a reduced and non-continuous address space. There are applications where this is fully acceptable (this thread is its prime example). I'd suggest to reformulate that note in all relevant DS to say this more precisely.

I also don't believe that FSMC_NE4 mapped at PC4 wouldn't work as expected in the 100-pin package, together with FSMC_NE1 at PD7, so I don't see a reason for the 'only 1 external memory' part of that note either.

And, as I said, I use an STM32F407VG in non-muxed mode, using only A18 to address two registers, while the same note can be found in the 'F407's DS, too.

And, while we are at this: the 'F407 DS contains a very nice and useful Table 8. FSMC pin definition which among other things displays also the availability of FSMC-related pins in the less-than-144-pin packages. I can't find this table's equivalent in the 'F413 DS... Said note than could point to that table for added clarity.

JW

PS. while the 'F413's FSMC is stripped-down so it does not contain the NAND part, there is a reference to it in RM0430 Rev.2 in ch.11.4...

thinkit z · ‎2017-02-22

Posted on February 23, 2017 at 07:54

I don't need a continuous address space.

OK, I think non-muxed will work, so I will try that later. The PCB hardware is not affected by non-muxed or muxed, if I connect all the related pins to FPGA. If I finish the job , I will come here to finish the discussion .

Other mcus with LQFP 100 pin maybe the same, for example , 41x 40x .f3x. f1x...etc.

thanks , all.

Amel NASRI · ‎2017-02-24

Posted on February 24, 2017 at 14:22

Hi Jan,

Your comments are reviewed carefully and actions will be taken into account to improve datasheet content in order to avoid confusion.

Thank you,

Amel

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Amel NASRI · ‎2017-02-24

Posted on February 24, 2017 at 14:24

Starting with CubeMX, it may be possible to select LCD Interface then add needed IOs.

-Amel

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stm32cube-t · ‎2017-03-10

Posted on March 10, 2017 at 15:26

Dear user,

Please note your remark will be taking into account as follows:

- update of the product documentation (Datasheet)

- update of STM32CubeMX solution to have the support for multiplexed interfaces on 64 and 81 pin packages (on F413, F423 and F412):

64 pins packages: support only 8 bit multiplexed mode interface

81 pins packages: support only 16bit multiplexed mode interface)

waclawek.jan · ‎2017-03-10

Posted on March 10, 2017 at 16:28

,

STM32Cube-T,

Thanks for letting us know.

- update of the product documentation (Datasheet)

While at it, could you please fix also

https://community.st.com/0D70X000006SI41SAG

. Thanks.

Jan Waclawek