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Adventurer
Adventurer
3,952 Views
Registered: ‎07-09-2012

Bit order

Hi to all,

I realized that reading from the register of a device using the OS installed on my ML605, the bit order is reversed. For example I would expect to read 10001101 instead i read 10110001.  I'm using Microblaze and a Linux OS.

 

Please, could someone help me?

 

BR,

Umberto.

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4 Replies
Visitor amitd
Visitor
3,893 Views
Registered: ‎08-26-2012

Re: Bit order

Which Bus are you using ? PLB or AXI?

Maybe its a Big - Little endian issue.

 

I'm using a PLB bus which is Big endian and for some registers the bit order reversed.

 

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Adventurer
Adventurer
3,877 Views
Registered: ‎07-09-2012

Re: Bit order

Hi amitd,

i'm using an AXI Bus.

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Visitor amitd
Visitor
3,830 Views
Registered: ‎08-26-2012

Re: Bit order

AXI bus should be little endian, but I don't have any experience with it.

Have you tried reading byte by byte and then comparing to reading a 32 bit?

 

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Visitor amitd
Visitor
3,829 Views
Registered: ‎08-26-2012

Re: Bit order

Also, have you confirmed this on several addresses?

Could it be that this address is for some HW peripheral that it's internal alignment is Big Endian?  

Try reading from other HW ip cores, see what you get.

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