2–16
Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
Transmitter Modules
Transmitter Local Clock Divider Block
The TX local clock divider blocks are located in each transmitter channels
of the transceiver block. The purpose of this block is to provide the
high-speed clock for the serializer and the low-speed clock for the
transmitter data path and the PLD for all the transmitters within the
transceiver block. This allows for each of the transmitter channels to run
at different rates. The /n divider offers a /1, /2, and /4 factors to provide
capability to reduce base frequency of the driving PLL to a half or a
quarter rate. This allows each transmitter channel to run at a /1, /2, or /4
of the original data rate.
Figure 2–7
shows the transmitter local clock divider block.
Figure 2–7. Transmitter Local Clock Divider Block
Each transmitter local clock divider block is operated independently, so
there is no guarantee that each channel sends out the same bit at the same
time.
Clock Synthesis
Each PLL in a transceiver block receives a reference clock and generates a
high-speed clock that is forwarded to the clock generator blocks. There
are two types of clock generators:
■
the transmitter local clock divider block
■
the central clock divider block
The transmitter local clock divider block resides in the transmit channel
and synthesizes the high-speed serial clock (used by the serializer) and
slow-speed clock (used by the transmitter’s PCS logic). The central clock
divider block resides in the transceiver block outside the transmit or
receive channels. This block synthesizes the high-speed serial clock (used
by the serializer) and slow-speed clock (used by the transceiver block PCS
logic—transmitter and receiver (if the rate matcher is used). The PLD
4, 5, 8, or 10
High-Speed
Clock to Transmitter
Slow-Speed
Clock to Transmitter
High-Speed Clock
From Transmitter PLL0
High-Speed Clock
From Transmitter PLL1
1, 2, or 4
n
÷
÷
÷