2–138
Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
Multiple Protocols and Data Rates in a Transceiver Block
The data rate range of single-width versus double-width mode is listed in
Table 2–31
. If the desired data rate range falls within a mode using the TX
local divider factors (/1, /2, or /4), you can use a single TXPLL to support
the desired data rate range. If the desired data rate range straddles two
modes, TXPLL sharing cannot be done. They can still be in the same
transceiver block, but you will need to use two TXPLLs.
In order to share a TXPLL, their PLL configurations are required to be the
same. The following is a list of TXPLL parameters that must be identical:
■
PLL bandwidth
■
Primary data rate
■
Reference clock frequency
■
Pre-divider on the dedicated
REFCLK
(if applicable)
Though the TXPLL settings must be identical, the TX local divider
settings on the channels can vary. You will need to set up the TXPLL for
the highest data rate and use the dividers to drop the data rate down on
the slower channels to /4 or /2 of the primary data rate. Use the
ALT2GXB MegaWizard to make your changes.
Non-Basic protocol modes cannot share a TXPLL unless they are all of the
same protocol and sub protocol.
1
TXPLL sharing is restricted to the channels within a transceiver
block.
Also, the analog buffer voltage setting
VCCH
must be the same across all
the channels in the transceiver block. The Quartus II software will not
allow channels with different
VCCH
settings into the same transceiver
block.
The following is an example of instances that can be combined into a
single transceiver block. We have two 4 Gbps, one 2 Gbps, and one
1 Gbps links. Since the target data rate is either a /1, /2, or /4 division
factor from the highest data rate, it is possible to combine this into a single
transceiver block. It is assumed that the
VCCH
, transceiver block signals
Table 2–31. Single-Width Versus Double-Width Data Rate Range
Mode
Minimum Data Rate
Maximum Data Rate
Single Width
600 Mbps
3.125 Gbps
Double Width
1 Gbps
6.375 Gbps