Released
Datasheet
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATM Traffic Management Device
11 APPLICATION NOTES
11.1 Connecting QRTs to QSEs Using Gigabit Ethernet Transceivers
QRTs can be connected to QSEs using Gigabit Ethernet transceivers. Several companies, includ-
ing AMCC and Vitesse Semiconductor Corporation, make Gigabit Ethernet transceivers. Vit-
esse has three devices: two old (the VSC7135 and the VSC7136) and one new (the VSC7214).
The PHY layer for Gigabit Ethernet is taken from Fiber Channel, so these devices are derived
from Fiber Channel devices.
The new VSC7214 is a quad device with integrated 8B/10B encoders. The information about the
new VSC7214 is at:
http://www.vitesse.com/news/052297.html
The existing VSC7135 and VSC7136 devices require an external 8B/10B encoder/decoder. The
web site for the existing VSC7135 and VSC7136 (and the VCS7214) is at:
http://www.vitesse.com/products/stdprod.html#1
The general interconnection method is to replace the first nibble of four cells with an 8B/10B
comma character, copying the Present (Pres) and Multicast (MC) cell bits of all four to the second
byte, and not sending the inverted Pres bit or the Spare (SP) bit. By doing this replacement, a full
byte is freed, leaving room for the comma character and allowing a simple interface. The SOC
signal then needs to be reproduced at the far end.
These serialization devices introduce significant latency, which eats into the one-celltime budget
for round-trip delay. Sending the BP_ACK_IN(3:0) signal without serialization helps reduce the
round-trip latency.
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PMC [ PMC-SIERRA, INC ]
