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What is the exact use of Wrapping burst transactions in AXI 4 ?

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achaleus

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Dear EDA Board members,

let us take one example with Burst Length=8, Number of Bytes=4 and Starting address=0x4a and data needs to be transferred using Wrapping Burst.

I have calculated the address of each transfer with respect to equations given in AMBA AXI Protocol Version 2.0 Specification.

the calculations are as follows,

Code:
Aligned Address = 0x48
Address_1=0x4a
Address_2=0x4c
Address_3=0x50
Address_4=0x54
Address_5=0x58
Address_6=0x5c
Address_7=0x60
Address_8=0x64

Wrap Boundary = 0x40

here Address_N = Wrap_Boundary + (Number_Bytes X Burst_Length) 
                        = 0x40 + (4*8) 
                        = 0x60
                        = Address_7
so Address_7 = Wrap Boundary =0x40.
then Address_8 will be 0x44.

The whole transaction looks like this

Code:
0x4B  0x4A  0x49  0x48 --- 1st transfer
0x4F  0x4E  0x4D  0x4C --- 2nd transfer
0x53  0x52  0x51  0x50 --- 3rd transfer
0x57  0x56  0x55  0x54 --- 4th transfer
0x5B  0x5A  0x59  0x58 --- 5th transfer
0x5F  0x5E  0x5D  0x5C --- 6th transfer
0x43  0x42  0x41  0x40 --- 7th transfer
0x47  0x46  0x45  0x44 --- 8th transfer

addr calc.JPG

Here for 7th and 8th transfer the address is changed to 0x40 and 0x44 respectively, which gives me the data that is not needed by me.(Garbage values)

So can any one please tell me the necessary and importance of using the Wrapping Burst type transactions?
 

jbeniston

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