GX4002 Datasheet, PDF (13/74 Pages) Gennum Corporation – Dynamic on-chip power management control

3. Detailed Description
3.1 Multirate CDR Functionality
There are two data rate ranges available for selection, so that a single part can be used
for multiple applications. The GX4002 does not require a reference clock. Some example
applications are as follows:
• 10Gb/s Ethernet (10.3Gb/s)
• 10Gb/s Ethernet with FEC (11.1Gb/s)
• 10G Fibre Channel (10.5Gb/s)
• 10G Fibre Channel with FEC (11.3Gb/s)
• Fibre Channel over Ethernet (10.3Gb/s)
• 16G Fibre Channel (14.025Gb/s)
Table 3-1: Mode Details
Mode
10G
14G
Description
The part will retime in a continuous range from 9.95Gb/s to 11.3Gb/s.
Through the serial interface, the part can be placed in 14G mode. In this
mode, the CDRs will retime at 14.025Gb/s, and is intended for use in 16G Fibre
Channel applications. An automatic rate detect circuit can be used that will
determine if the incoming data rate is a legacy Fibre Channel rate, and will
automatically bypass the CDRs. By using the automatic rate detect feature,
RS0 and RS1 pins are not required. The automatic rate detect feature is not
enabled by default when the device is configured in 14G mode.
3.1.1 Rate Selection and Rate Detection
The GX4002 has three different methods to select the data rate. The rate can be selected
through the use of the RS0/RS1 pins, through the use of registers, or through automatic
detection. The rate selection methods are described in more detail below.
The GX4002 also contains a set of data-dependent registers. This enables parameters
such as rise and fall times to be automatically configured based on the data rate. There
are two profiles, one for low data rates such as 4G or 8G Fibre Channel, and one for high
data rates such as 10GbE or 16G Fibre Channel. The register map (Appendix:
Configuration and Status Register Map) shows which registers contain both low data
rate and high data rate options.
A configuration profile is invoked by one of three methods:
1. Using input pins RS0 and RS1 to invoke a “hard” rate select for either the Ch0 path
or Ch1 path respectively (CH0PLLRATESELVAL is HIGH and/or
CH1PLLRATESELVAL is HIGH).
2. Using host interface commands to invoke a “soft” rate select for either the Ch1 or
Ch0 path, or for both Ch1 and Ch0 paths together using the CH1PLLRATESEL and
CH0PLLRATESEL bits (CH1PLLRATESELVAL is HIGH and/or
CH0PLLRATESELVAL is HIGH).
GX4002 2x2 14.025Gb/s Crosspoint Switch with Trace
Equalization and Output De-Emphasis
Data Sheet
55972 - 0
March 2012
13 of 74
Proprietary & Confidential