Altera SerialLite II Protocol - Manual (Page 42)

42 Altera Corporation
SerialLite II Protocol Reference Manual
Data Link Layer Description
Figure 2–21. Idle Inserted When User Packet Is Interrupted
4. The IDL symbol is used to fill the idle lanes when a portion of a
column is idle before an end of packet.
Data Transmission Priority
The following is a list of the priority order for all data transfers:
1. Clock compensation sequence
2. Training patterns
3. Link management packet—flow control
4. Link management packet—retry-on-error
5. User priority packet
6. User data packet
7. Idles
Nesting Packets
To reduce delays in transmitting time-critical control packets, SerialLite II
inserts high priority packets into a data packet that is already in
transmission (nests the packets). Link management packets have the
highest packet priority and do not require an escape sequence before
insertion.
Figure 2–22 on page 2–43 shows the double-nesting of a link
management packet inside a user priority packet, which in turn is nested
in a user data packet.
SDP User Data EGP User Data Idle Idle Idle
Interruption (or under-run)
at the system interface