AXI

Question 1

Transaction

Answer 1

A master initiates a transaction to communicate with a slave. Typically, the transaction requires information to be exchanged between the master and slave on multiple channels.
The complete set of required exchanges form the transaction.

Question 2

Unaligned

Answer 2

An unaligned access is an access where the address of the access is not aligned to the size of an element of the access.

Question 3

Aligned

Answer 3

A data item stored at an address that is divisible by the highest power of 2 that divides into its size in bytes.

Aligned halfwords, words and doublewords therefore have addresses that are divisible by 2, 4 and 8 respectively.

An aligned access is one where the address of the access is aligned to the size of each element of the access.

Question 4

Beat

Answer 4

An individual data transfer within an AXI burst.

Question 5

Burst

Answer 5

Payload data comprising multiple, individual data transfers (beats).

Question 6

ARM Word size?

Answer 6

32 bits. Words are normally word-aligned in ARM systems.