Altera Corporation
2–17
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
clock is also supplied by the central clock divider block and goes through
the divide-by-two block (located in the central block of the transceiver
block) if the byte serializer/deserializer is used.
The PLLs in the transceiver have half rate VCOs that run at half the rate
of the data stream. When in the individual channel mode, the slow-speed
clocks for the transmitter logic and the serializer need only be
/
4 or a
/
5
divider to support a ×8 and ×10 serialization factor. The ×16 and ×20
serialization factor is supported by the
/
8 and
/
10 clock divider.
Table 2–4
shows the divider settings for achieving the available serialization factor.
In the four-lane mode, the central clock divider block supplies all the
necessary clocks for the entire transceiver block.
The reference clock ranges from 50 MHz to 622.08 MHz. The phase
frequency detector (PFD) has a minimum frequency limit of 50 MHz and
a maximum frequency limit of 325 MHz.
The
refclk
pre-divider (/2 ) is available if you use the dedicated
refclk
pins for the input reference clock. The
refclk
pre-divider is
required if
one
of the following conditions is satisfied:
1.
If the input clock frequency is greater than 325 MHz.
2.
For functional modes with a data rate less than 3.125 Gbps (the data
rate is specified in the
what is the data rate?
option in the
General
tab of the ALT2GXB MegaWizard):
●
If the input clock frequency is greater than or equal to 100 MHz
AND
●
If the ratio of data rate to input clock frequency is 4, 5, or 25
Table 2–4. Serialization Factor and Divider Settings
Serialization Factor
Divider Setting
× 8
/
4
× 10
/
5
× 16
/
8
× 20
/
10