Altera Corporation
2–123
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
The PLD interface clock utilization can be further reduced by directly
feeding the
tx_coreclk
and/or the
rx_coreclk
ports of like channels
directly with a single clock. The source clock must be frequency locked to
the associated transceiver output clock. Any PPM difference results in
data corruption.
To help guard against incorrect usage, the use of the
tx_coreclk
and
rx_coreclk
options requires clock assignments in the assignment
organizer. If no assignments are used, the Quartus II software will give a
compilation error.
There are 4 settings to enable the PLD interface clocking options:
■
Stratix II GX GXB Shared Clock Group Setting
■
Stratix II GX GXB Shared Clock Group Driver Setting
■
Stratix II GX 0PPM Clock Group Setting
■
Stratix II GX 0PPM Clock Group Driver Setting
As the name indicates, there are two main settings, each with a driver and
clock group setting. When specifying clock groups, an integer identifier is
used as the group name in order to differentiate other clock group
settings from one another.
The
Stratix II GX GXB Shared Clock Group Setting
is the safest
assignment. The Quartus II compiler will analyze the netlist during
compilation to ensure TX channel members are derived from the same
source. The Quartus II software will give a fitting error for incompatible
assignments. The software cannot check for the output of the RX
frequency locked to the driving clock as the exact frequency is dictated by
the upstream transmitter's source clock. It will be up to you to ensure that
the
rx_coreclk
is derived from the same source clock as the upstream
transmitter.
The
Stratix II GX GXB Shared Clock Group Driver Setting
assignment
must be made to the source channel of the
tx_clkout
or
coreclk_out
.
Specifying anything except the TX channels (the source for the
tx_clkout
or
coreclk_out
) will result in a fitter error. If the source
clock is not from
tx_clkout
or
coreclk_out
(for example, the source
is from
rx_clkout
or from a PLD clock input), the 0 PPM setting must
be used instead.
For example, in a synchronous system, the TX and RX are of the same data
rate and configuration. The clock output of the channel 0 is used (but any
TX clock output can be used). The
Stratix II GX GXB Shared Clock
Group Driver Setting
is made in the assignment editor on the
tx_dataout[0]
name. You can use a group identifier value of "1" to
identify the group that this driver feeds. The
Stratix II GX GXB shared