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Hi
I have a simple memory test routine that I run on Ethernet SRAM (16K) - which works fine, e.g. 1) Passes 16K and not a byte more 2) Fails when accessing past 16K 3) RAM fails, as it should when Ethernet controller power is not enabled via PCONP.30 (as per Phillips Errata Ethernet.2)
However, same routine on USB's 8K SRAM works as follows: 1) Works even if the USB power not enabled (bit 31 on PCONP) 2) Passes more than 8K, in fact up to 16K. In other words, there seems to be some addressable memory at addresses 0x7FD02000-0x7FD03FFF, which is not documented.
It may be writing to some other memory, like a region the main SRAM?
I have confirmed that it is not overwriting 16K of Ethernet SRAM.
Test routine is a simple "write a pattern and then read it back" test.
I know this sounds unlikely, so does anybody have any thoughts?
Cheers
To use USB RAM you dont have to turn on USB power. For ethernet it was in errata to turn on the power.
The 8 K USB RAM may be shadowed. Try writing different pattern at the startup of the 8 Kblock and read it back to know that the two locations are physically different.
I dont see any reason for NXP not advertising that RAM (If at all it is their physically) in any of the 23xx versions.
Regards
Suvidh
Hi Suvidh
"Try writing different pattern at the startup of the 8 Kblock and read it back to know that the two locations are physically different"
This is exactly what I am doing, writing a pattern to entire 16K, in such a way that values are different in lower and the upper 8K, then reading it back.
Thanks
Michael