Benefiting from EMAC Buffer Descriptor operation in little-endian mode [K70 / K61]

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Benefiting from EMAC Buffer Descriptor operation in little-endian mode [K70 / K61]

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mjbcswitzerland
Specialist V

Hi All

 

The K70 and K61 (maybe others) have the capability of configuring the Ethernet EMAC's buffer descriptors to operate in native little-endian mode rather than the basic big-endian mode. This allows software to avoid having to do little-endian/big-endian swapping and thus results in optimised code.

 

To adjust existing Ethernet code to benefit from this when a suitable Kinetis type is used is quite easy. The following is an example of how it can be performed using some conditional defines:

 

http://www.utasker.com/forum/index.php?topic=1752.msg6274#msg6274

 

Regards

 

Mark

 

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ndavies
Contributor V

This configuration bit now appears in the K60 documentation. It's in the 120 and 150 Mhz part's RMs and also appeared in the V2 of the 100mhz RM. It wasn't in the original K60 RM.

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mjbcswitzerland
Specialist V

Hi

 

At the moment I haven't been able to work out exactly which chips can and can't do this.

 

If the K60 is named something like MK60DN256VLQ10 it can according to the V2 reference manual.

If it is names something like MK60DN256ZVLQ10 it doesn't seem to be able to according to the orignal reference manual.

 

However, no data sheets mention the Z as a valid part identification (there shouldn't be this field according to the part identification format defined in either old or new data sheete). So it is presently a mystery.

 

Approaching this practically, when tried on a PK60N512LVMD100 it fails when attempted with this configuration, although I don't know where thsi one would fit in - it is a prequaltification part but doesn't have the Z (?). K70 parts do work, as expected - probably also 120/150M parts with FPU will too...

 

Therefore best to test quickly with the chip that will be used for production and then keep it enabled if it does work (trial and error :smileywink:

 

Regards

 

Mark

 

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