S32 SDK中的主题 Re: Questions about FlexRAM

Questions about FlexRAM

kmh48301 — Fri, 04 Sep 2020 01:08:59 GMT

I'm using S32k144.

I got two questions studying EEE

1. FlexRAM is slower than SRAM

Please see this picture . (it's from AN11983 p11)

When I see flash memory map, I think FlexRAM is also contiguous addresses.

but this is saying non-contiguous...

and is that why the FlexRAM is slower than SRAM?

FlexRAM is not static RAM?

2. "a background pattern of all ones" ???

I saw "a background pattern of all ones" several times in NXP documents..

But I have no idea what it means since I'm not native English speaker,,

Please explain to me

Thanks

Best regards,

Phillip

danielmartynek — Mon, 07 Sep 2020 07:45:43 GMT

Hello Phillip,

Please refer to the RM, rev.12.1, Section 31.3.2 SRAM accessibility

"To supplement the main system RAM, FlexRAM can be used as system RAM. However,
FlexRAM accesses involve additional system latencies."

This is because FlexRAM is not tightly coupled with the core.

As you can see below, the FlexRAM is a slave on the Crossbar switch.

The SRAM_L and SRAM_U regions are contiguous, mapped right next to each other.

But FlexRAM starts at 0x14000000.

A2.

That simply means that the FlexRAM is initialized with all ones, like each 32b word is written with 0xFFFFFFFF.

Regards,

Daniel

kmh48301 — Mon, 07 Sep 2020 23:13:55 GMT

Thanks Daniel. I understood.