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Altera_Forum's avatar
Altera_Forum
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8 years ago

What if startofpacket is deasserted before endofpacket?

The concept of data packet usually involves a stream of serial data with fields. A data packet thus becomes a self contained unit and may not have a total fixed length as some fields may be of variab...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
8 years ago

Lots of things could arrise:

1. Data loss, you've lost some data - how do we resync with the start of a packet?

2. Data corruption - CRC fails, something is wrong in the packet

3. You didnt receive an EOP and you've got data loss - what now?

You can use SOP/EOP to resynchronise your state machine should the above things occur.

Now - what if we are just sending some data thats not got any headers that tell us the packet length?

Avalon (and AXI) are format agnostic. They dont care what you send over them. So SOP/EOP are just optional signals that dont need to be used, but all the Altera IPs require them to be there, for the above reasons.

If you get 2 SOPs with no EOP, there was probably a problem upstream. You need to decide how to fix that - fix the upstream block, or design the system so that is impossible.