ep1agx50d Altera Corporation, ep1agx50d Datasheet - Page 30

• Manufacturer Part Number: ep1agx50d
• Description: Arria Gx Device Data Sheet
• Manufacturer: Altera Corporation

Transceivers
2–22
Arria GX Device Handbook, Volume 1
Table 2–5
can tolerate in XAUI, PCI Express (PIPE), GIGE, and Basic functional
modes.
XAUI Mode
In XAUI mode, the rate matcher adheres to clause 48 of the IEEE 802.3ae
specification for clock rate compensation. The rate matcher performs
clock compensation on columns of /R/ (/K28.0/), denoted by //R//.
An //R// is added or deleted automatically based on the number of
words in the FIFO buffer.
PCI Express (PIPE) Mode Rate Matcher
In PCI Express (PIPE) mode, the rate matcher can compensate up to
± 300 PPM (600 PPM total) frequency difference between the upstream
transmitter and the receiver. The rate matcher logic looks for skip ordered
sets (SOS), which contains a /K28.5/ comma followed by three /K28.0/
skip characters. The rate matcher logic deletes or inserts /K28.0/ skip
characters as necessary from/to the rate matcher FIFO.
The rate matcher in PCI Express (PIPE) mode has a FIFO buffer overflow
and underflow protection. In the event of a FIFO buffer overflow, the rate
matcher deletes any data after detecting the overflow condition to
prevent FIFO pointer corruption until the rate matcher is not full. In an
underflow condition, the rate matcher inserts 9'h1FE (/K30.7/) until the
FIFO buffer is not empty. These measures ensure that the FIFO buffer can
gracefully exit the overflow and underflow condition without requiring a
FIFO reset. The rate matcher FIFO overflow and underflow condition is
indicated on the pipestatus port.
You can bypass the rate matcher in PCI Express (PIPE) mode if you have
a synchronous system where the upstream transmitter and local receiver
derive their reference clocks from the same source.
Table 2–5. Rate Matcher PPM Tolerance
PCI Express (PIPE)
shows the maximum frequency difference that the rate matcher
Function Mode
GIGE
Basic
XAUI
± 100
± 300
± 100
± 300
PPM
Altera Corporation
May 2008