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LPC 1857 EMC Bus Timing & Static Parallel Flash

Question asked by James Tasker on Mar 27, 2018
Latest reply on Mar 29, 2018 by James Tasker

Hello,

I'm using the Keil MCB1800 development board (LPC1857) and am trying to use the NOR parallel flash for data storage. The flash chips are Spansion S29GL064N90TFI020 and there are two of them to for a 32-bit bus.  I'm using the Cypress/Spansion supplied low-level-driver to attempt to access the memory.  I'm running the EMC bus at 90 MHz and the processor at 180 MHz. 

 

The issue I'm seeing is that the commands that I send to the external flash, are not sent out on the EMC bus in the same order that they are designed to go out in code, or some commands are skipped all together (verified by scope).  I believe this may be because the processor is running much faster than the EMC and therefore the EMC cannot keep up with the data that it is supposed to send out??? If this is the case, what is the best practice and most efficient way to code up sequential commands (WR, RD, WR) or (WR, WR, WR, WR, WR, RD) to make sure they are being delivered or performed in the proper order?  I've tried waiting for the B and S bits in the EMC STATUS register to be clear before sending the next command, but this does not fix the issue.

 

Any thoughts or pseudo-code to help me get going would be fantastic.  Also, I'm new to using NOR static memory, so any good resources or example code of using/accessing external parallel flash in firmware would be appreciated (I couldn't find any examples that use/access the external parallel flash for the MCB1800).

 

Thanks in advance for your time.

 

-Jim

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