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LPC4320 I2C issue when running from RAM

Question asked by Pete James on Apr 12, 2017
Latest reply on Apr 18, 2017 by jeremyzhou

Hello,

 

We have an application which uses the LPC4320 which, up to now has been running out of external flash using SPIFI. Periodically (every 1s) the code writes a DWORD to a FRAM memory device on I2C0. Everything works correctly, no issues.

 

We have now added the header to the image in the external FLASH IC so the CPU copies the application out of the external FLASH and into the RAM on the CPU and executes it from there. The code runs a lot faster now but the reads or writes to/from the I2C FRAM chip fail.

 

We are investigating how it fails but so far (we haven't an I2C protocol analyser yet) when running from SPIFI there is a gap of about 5uS between the bytes on the I2C bus but when running out of RAM there doesn't appear to be any gaps.

 

FRAM memory is similar to EEPROM but you can do many billions of writes and the writes/reads are as fast as you can read/write them. You don't need to check the byte has been written before sending the next.

 

Anyone any ideas on why it should work OK out of SPIFI and not out of RAM?

 

Many thanks

Pete

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