lpcware

External SDram read consistently slower than write

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by fguerzoni on Wed Oct 08 16:10:34 MST 2014
Hi,
I have a strange issue with LPC4357 + 256M-AS4C16M16S (16x16x4) sdram memory on custom board.
When using GPDMA:
- Writes from local ram (any bank) to external ram are at 185MByte/sec
- Reads from external ram to local ram (any bank) are at   75MByte/sec
Theoretical speed limit is 204MByte/sec (ram clock is 102MHz and bus is 16bit)

When using direct memcpy things go slowly but writes happens with double the reads speed.

No errors happens on data at all but I think I'm missing something macro because I think reads should be at least fast as writes.

I doubled checked configurations and application code without results.
Thanks in advance for any suggestion.

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