Remap in FMC

[Christophe Chaloin]

Posted on October 04, 2017 at 18:15

Reading the reference manual of STM32F4xx (RM0090), I need some explanation about the physical remap in FMC.

Page 71-72, �2.4, the interpretation of table 4 is not clear. Should I understand that when in mode Remap in FMC:

if MEM_MODE=010b (SYSCFG �9.3.1 page 298) :

NOR/PSRAM bank1 (64MB) goes from 0x0000 0000 to 0x03FF FFFF

and

NOR/PSRAM bank2 (64MB) goes from 0x0400 0000 to 0x07FF FFFF

and if MEM_MODE=100b (SYSCFG �9.3.1 page 298) :

the lower 128MB (out of 256MB) of SDRAM 1 are mapped from 0x0000 0000 to 0x07FF FFFF

(and the upper 128MB of SDRAM 1 are not accessible)

Because what I read in Table 4 doesn't look logical / correct. How does it exactly work ?

Thank you !

#stm32f4 #fmc #remap

[Tilen MAJERLE]

Posted on October 05, 2017 at 10:32

Hello Christophe,

can you please provide more info what does not look correct to you?

Best regards,

Tilen

[Christophe Chaloin]

Posted on October 05, 2017 at 11:52

Hello Tilen,

Table 4, page 72, when Remap in FMC mode:

* memory section 1, range 0x0400 0000 - 0x07FF FFFF: FMC bank 1 NOR/PSRAM 2 (128 MB aliased)

This range is 64MB.

NOR/PSRAM 2 is 64MB too and then can be remapped there. So Why this comment about '128 MB aliased' ?

* memory section 0, range 0x0000 0000 - 0x03FF FFFF: FMC bank 1 NOR/PSRAM 1 (128 MB aliased)

                                                                                               or FMC SDRAM bank 1 (128 MB aliased)

This range is also 64MB.

It can be mapped to PSRAM 1 which is also 64 MB. So why is it noted '128MB aliased' ?

With FMC SDRAM bank 1 (which is 256 MB), if 128MB are aliased, it should map both blocs (0x0000 0000 - 0x07FF FFFF).

Then only half of the 256MB SDRAM bank 1 can be mapped (I assume that this is the lower part). So why there is no reference to SDRAM bank 1 in the comment of memory section 1 (0x0400 0000 - 0x07FF FFFF) ?

Regards,

Christophe