Altera RapidIO MegaCore Function - Manual (Page 63)

Chapter 4: Functional Description 4–17
Physical Layer
August 2014 Altera Corporation RapidIO MegaCore Function
User Guide
Figure 4–6 shows sample threshold values in context to illustrate how they work
together to enforce the deadlock prevention rules.
Physical Layer Transmit Buffer
The Physical layer accepts packet data from the Transport layer and stores it in the
transmit buffer for the RapidIO link low-level interface transmitter. The data passes
from the Transport layer to the Physical layer on a bus that is 32 bits wide in 1x
variations and 64 bits wide in 2x and 4x variations.
The transmit buffer implements the following features:
■ Provides clock decoupling between the Transport layer sysclk clock domain and
the Physical layer txclk clock domain.
■ Implements the RapidIO specification requirements for packet priority handling
and deadlock avoidance, by configuring individual priority transmit and
retransmit queues.
Figure 4–6. Receiver Threshold Levels
Start retrying priority 0 packets
Start retrying priority 1 packets
Priority 0 Threshold
Priority 1 Threshold
Priority 2 Threshold Start retrying priority 2 packets
Retry priority 3 packets Buffer Full