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S32R274 Can't get DMEM(TCM) to operate anything near CPU clock Speed ?

Question asked by mark thompson on Jan 19, 2018
Latest reply on Feb 12, 2018 by mark thompson

I'm having trouble getting the DMEM to work at speed.

The spec says "Access latency (zero wait-states) is similar to that of a data cache"

My tests show that I am able to access the local DMEM at only 25% faster than main memory with the D-Cache Disabled.

When D-Cache is enabled it jumps 200% faster relative to Disabled cache, this indicates that the DMEM is being cached ?

This does not make sense unless the access are going the main AHB bus.

 

I have checked DCR 496 (DMEMCTL0)and it shows defaults.0x41B.

 

I changed it to not bypass decorated access 0x01B, no speed change.

 

I changed it to not bypass decorated access and disable ECC checking 0x00, no speed change.

 

Any idea what is happening here ?

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