Altera RapidIO II MegaCore Function - Manual (Page 90)

4–48 Chapter 4: Functional Description
Logical Layer Interfaces
RapidIO II MegaCore Function August 2014 Altera Corporation
User Guide
Avalon-ST Pass-Through Interface
The Avalon-ST pass-through interface is an optional interface that is generated when
you select the Avalon-ST pass-through interface in the Transport and Maintenance
page of the RapidIO II parameter editor (refer to
“Enable Avalon-ST Pass-Through
Interface” on page 3–3 ).
The Avalon-ST pass-through interface supports the following applications:
■ User implementation of a RapidIO function not supported by this IP core (for
example, data message passing).
■ User implementation of a custom function not specified by the RapidIO protocol,
but which may be useful for the system application.
After packets appear on your RapidIO II IP core Rx Avalon-ST pass-through interface,
your application can route them to a local processor or custom user function to
process them according to your design requirements.
Transaction ID Ranges
To limit the required storage, the RapidIO II IP core shares a single pool of transaction
IDs among all destination IDs, although the RapidIO specification allows for
independent pools for each Source-Destination pair.
To simplify the routing of incoming ftype=13 response packets, the IP core assigns an
exclusive range of transaction IDs to each of the instantiated Logical layer modules.
This set of assignments simplifies response routing, but places a constraint on your
design. If you implement custom logic that communicates to the RapidIO II IP core
through the Avalon-ST pass-through interface, you must ensure your logic does not
use a transaction ID assigned to another instantiated Logical layer module for
transmitting request packets that expect an ftype=13 response packet. If you use such
a transaction ID, the response will be routed away from the Avalon-ST pass-through
interface and your custom module will never receive the response.
Table 4–23 shows the transaction ID ranges assigned to various Logical layers.
The RapidIO II IP core Transport layer routes response packets of ftype=13 with
transaction IDs outside the 64–143 range to the Avalon-ST pass-through interface.
Your system should not use transaction IDs in the 0-63 range if the Maintenance
Logical layer Avalon-MM slave module is instantiated, because their use might cause
the uniqueness of transaction ID rule to be violated.
Table 4–23. Transaction ID Ranges and Assignments
Range Assignments
0–63
This range of Transaction IDs is used for ftype=8 responses by the Maintenance Logical layer
Avalon-MM slave module.
64–127
ftype=13 responses in this range are reserved for exclusive use by the Input-Output Logical layer
Avalon-MM slave module.
128–143 ftype=13 responses in this range are reserved for exclusive use by the Doorbell Logical layer module.
144–255
This range of Transaction IDs is currently unused and is available for use by Logical layer modules
connected to the pass-through interface.