Question on T4.1 Serial Flash (U3)

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joepasquariello

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I'm confused about flash on the T4.1. It has the same iMXRT1062 as T4.0, so it must have the same 2 MB on-chip flash. It also has 8 MB serial flash (W25U64) chip on U3, so doesn't it have 10 MB flash, as opposed to 8 MB as shown in specs? I understand the pads on the bottom accommodate optional PSRAM and Flash. Is code stored in the on-chip flash, the same as T4.0? Is the serial flash (U3) accessible for application data storage, or is it somehow used for code storage? Thanks very much.
 
Teensy 4.0 also has a flash chip, also U3, part number W25Q16JVUXIM.


Is the serial flash (U3) accessible for application data storage, or is it somehow used for code storage?
Click to expand...

A portion of the chip is reserved for EEPROM emulation, using the EEPROM library.

Starting with version 1.54 (currently in beta testing) you can also use part of the unused program memory space for file storage, using LittleFS_Program.
 
Thanks, Paul. I'm still unclear on why the T4.1 page says it has 8 MB of flash and not 2+8 = 10 MB. For code space, it has the same 2MB on-chip flash as T4.0, plus the 8MB U3 for EEPROM + future stuff?
 
Each board has 1 flash chip.

I'm still unclear on why the T4.1 page says it has 8 MB of flash and not 2+8 = 10 MB.
Click to expand...

You've misunderstood. Check the schematics again. Each board has 1 flash chip, 8MB on Teensy 4.1, 2BM on Teensy 4.0. The specs on the product pages are accurate.
 
Ah, light dawns on Marblehead. Thank you. I thought the 2MB of flash on T4.0 was on-chip. Now I understand there is only the external serial flash, 2MB for T4.0, 8MB for T4.1. How interesting. I need to read up on the XIP capability.
 
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