• State Suggested Answer
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 350 subscribers
  • Views 5525 views
  • Users 0 members are here
Options
Related
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

AXI4 Narrow and possibly unaligned READ

af_23

Hi.

I have a 16-byte AXI4 data bus.

I want to read 3 bytes, and there's a limitation to only use INCR burst. 

I know that AXI only supports 1,2,4,8, etc byte-size bursts, but I have another module to receive the data from AXI and extract only the desired 3 bytes.

Length 0 (1 beat) is enough obviously.

Let's say the read address is 0x4a7a.

My question is, what is the correct ARSIZE for this read request?

I originally thought that SIZE = 0x2 (4 bytes) is the answer, exemplified below:

this Access is not aligned.

0xF 0xE 0xD 0xC 0xB 0xA 0x9 0x8 0x7 0x6 0x5 0x4 0x3 0x2 0x1 0x0
V V V V

But I guess that SIZE = 0x3 (8 bytes) is also possible:

0xF 0xE 0xD 0xC 0xB 0xA 0x9 0x8 0x7 0x6 0x5 0x4 0x3 0x2 0x1 0x0
V V V V V V

this Access is not aligned as well

Is there one better than the other? is one of them illegal?

Thanks