Altera Arria V GZ Avalon-ST - Manual (Page 166)

Tracing a transaction through the TX datapath involves the following steps:
1. The Transaction Layer informs the Application Layer that sufficient flow control credits exist for a
particular type of transaction using the TX credit signals. The Application Layer may choose to ignore
this information.
2. The Application Layer requests permission to transmit a TLP. The Application Layer must provide the
transaction and must be prepared to provide the entire data payload in consecutive cycles.
3. The Transaction Layer verifies that sufficient flow control credits exist and acknowledges or postpones
the request.
4. The Transaction Layer forwards the TLP to the Data Link Layer.
Figure 10-2: Architecture of the Transaction Layer: Dedicated Receive Buffer
Transaction Layer TX Datapath
Transaction Layer RX Datapath
Avalon-ST
RX Control
Configuration Space
TLPs to
Data Link Layer
RX Transaction
Layer Packet
Avalon-ST RX Data
Avalon-ST
TX Data
to Application Layer
ConfigurationRequests
Reordering
RX Buffer
Posted & Completion
Non-Posted
Flow Control Update
Transaction Layer
Packet FIFO
Width
Adapter
( <256
bits)
Packet
Alignment
TX
Control
RX
Control
TX Flow
Control
10-6 Transaction Layer
UG-01127_avst
2014.08.18
Altera Corporation IP Core Architecture
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