Altera Mentor Verification IP Altera Edition AMBA AXI4-Lite - Manual (Page 22)

Mentor Verification IP AE AXI4-Lite User Guide, V10.3 22
Mentor VIP Altera Edition
What Is a Transaction?
April 2014
What Is a Transaction?
A transaction for Mentor VIP AE represents an instance of information that is transferred
between a master and a slave peripheral, and that adheres to the protocol used to transfer the
information. For example, a write transaction transfers an address phase, a data a phase,
followed by a response phase. A subsequent instance of transferred information requires a new
and unique transaction.
Each transaction has a dynamic Transaction Record that exists for the life of the transaction.
The life of a transaction record starts when it is created and ends when the transaction
completes. The transaction record is automatically discarded when the transaction ends.
When created, a transaction contains transaction fields that you set to define two transaction
aspects:
•
Protocol fields are transferred over the protocol signals.
•
Operation fields determine how the information is transferred and when the transfer is
complete.
For example, a write transaction record holds the protection information in the prot protocol
field; the value of this field is transferred over the AWPROT protocol signals during an address
phase. A write transaction also has a transaction_done operation field that indicates when the
transaction is complete; this field is not transferred over the protocol signals. These two types of
transaction fields, protocol and operation, establish a dynamic record during the life of the
transaction.
In addition to transaction fields, you specify arguments to tasks, functions, and procedures that
permit you to create, set, and get the dynamic transaction record during the lifetime of a
transaction. Each BFM has an API that controls how you access the BFM transaction record.
How you access the record also depends on the source code language, whether it is VHDL or
SystemVerilog. Methods for accessing transactions based on the language you use are
explained in detail in the relevant chapters of this user guide.
AXI4-Lite Transactions
A complete read/write transaction transfers information between a master and a slave
peripheral. Transaction fields described in “
What Is a Transaction? ” on page 22 determine what
is transferred and how information is transferred. During the lifetime of a transaction, the roles
of the master and slave ensure that a transaction completes successfully and that transferred
information adheres to the protocol specification. Information flows in both directions during a
transaction with the master initiating the transaction, and the slave reporting back to the master
that the transaction has completed.
An AXI4-Lite protocol uses five channels (three write channels and two read channels) to
transfer protocol information. Each of these channels has a pair of handshake signals, *VALID