Other RP2040 boards • Re: RP2350B: Huge min_deselect with PSRAM + Flash

Are you using DMA?
P.S. Have you checked the data integrity at that alleged 250MHz?

Yes, I’m checking it both through regular pointer-based reads/writes to uncached memory and through DMA (also uncached). The speed tests are done with DMA, and the data passes the integrity checks.

Also I see in LY68L6400 datasheet
tCPH CE# HIGH between subsequent burst operations 50ns

Exactly! And 50 ns is completely sufficient when working without flash involved (that gives around 7–8 min_deselect). But when I’m running code from flash, I suddenly need about 253 ns. That’s why I think the issue is specifically in the device switching.
It’s very strange.

Statistics: Posted by nightrain912 — Mon Nov 24, 2025 9:20 am

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