Can someone advice a psram for STM32F479 LQFP100 ?

[Dany1]

Dear Community,

can someone advice a min 8Mbit psram for the STM32F479?

I only find some who has address pins up to A20 but the uc has only up to 16 or did I missunterstand something?

best regards

[Imen.D]

Hello @Dany​ ,

Which package are you using ?

It depends on the package that you are used.

You can check the PSRAM configuration and address max with STM32CubeMX.

For example, with LQFP100 package : Max 16 bits for Muxed PSRAM.

You can refer to the Table 10. STM32F479xx pin and ball definitions in the STM32F479xx datasheet to check the PSRAM address pins.

Imen

[Dany1]

Sorry - I have to use the STM32F479 in LQFP100 package but somehow I can't find any PSRAM with up 8Mbit+ which can be used.. or I missunderstand how it should work.

Hopefully you can help me to get in the rigth direction.

EDIT: Am I right that if I use this RAM I'm only able to use 128 kbyte by leaving A16-A18 unconnected / gnd?

So it looks like its not possible to drive 400 x 600 display with that package?

Thanks

[M.Hajji · Accepted solution]

Hello @Dany​,

I suggest to look at AN4861, Table 20 "Example of graphic implantations with STM32 in different hardware configurations", for 400x600 I think at least you need LQFP144 package and with LQFP100 you should aim for low end display configuration.

For the PSRAM with STM32F479 LQFP100, you need a ADMUX Pseudo SRAM (support a multiplexed address/data bus) for example AS1C4M16PL-70BIN but with the STM32F479 LQFP100 you don't have the upper address signals available (A[21:16]), so you only have 16 address signals to work with.

To calculate the size of the memory knowing number of address lines and data width you have the formula:

Size = (2^(number of address lines)) * data width

For example, the one you attached have 19 address line and 16bit data width so:

(2^19) * 16bit = 512K * 16 = 8Mbit

and in the case of F479 LQFP100 you have:

(2^16) * 16bit = 64K * 16 = 1Mbit

Hope this help.

Regards,

Mahmoud.