Altera RapidIO MegaCore Function - Manual (Page 68)

4–22 Chapter 4: Functional Description
Logical Layer Modules
RapidIO MegaCore Function August 2014 Altera Corporation
User Guide
Response packets of ftype=13 with transaction IDs outside the 64–143 range are
routed to the Avalon-ST pass-through interface. Transaction IDs in the 0-63 range
should not be used 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.
If the Input-Output Avalon-MM slave module or the Doorbell Logical layer module is
not instantiated, response packets in the corresponding Transaction IDs ranges for
these layers are routed to the Avalon-ST pass-through interface.
Transmitter
On the transmit side, the Transport layer module uses a round-robin scheduler to
select the Logical layer module to transmit packets. The Transport layer polls the
various Logical layer modules to determine whether a packet is available. When a
packet is available, the Transport layer transmits the whole packet, and then continues
polling the next logical modules.
In a variation with a user-defined Logical layer connected to the Avalon-ST
pass-through interface, you can abort the transmission of an errored packet by
asserting the Avalon-ST pass-through interface gen_tx_error signal and
gen_tx_endofpacket
.
f For more information about the Transport layer, refer to Part 3: Common Transport
Specification of the RapidIO Interconnect Specification, Revision 2.1.
Logical Layer Modules
This section describes the features of the Logical layers, and how they integrate and
interact with the Transport and Physical layers to create the three-layer RapidIO
protocol.
Figure 4–8 shows a high-level block diagram of the Logical layer, which
consists of the following modules:
■ Concentrator module that consolidates register access.
■ Maintenance module that initiates and terminates MAINTENANCE transactions.
■ I/O slave and master modules that initiate and terminate NREAD, NWRITE, SWRITE,
and NWRITE_R transactions.
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.
Table 4–4. Transaction ID Ranges and Assignments (Part 2 of 2)
Range Assignments