Figure 2-19: Six Identical Channels with a Single User-Selected Transmitter Interface Clock
FPGA Fabric
Transceivers
Channel 7
Channel 6
Channel 5
Channel 4
Channel 3
Channel 2
Channel 1
Channel 0
tx_coreclkin[6]
Channel [7:0] Transmitter
Data and Control Logic
tx_coreclkin[5]
tx_coreclkin[4]
tx_coreclkin[3]
tx_clkout[4]
tx_coreclkin[7]
tx_coreclkin[1]
tx_coreclkin[0]
tx_coreclkin[2]
To clock six identical channels with a single clock, perform these steps:
1. Instantiate the
tx_coreclkin
port for all the identical transmitter channels (
tx_coreclkin[5:0]
).
2. Connect
tx_clkout[4]
to the
tx_coreclkin[5:0]
ports.
3. Connect
tx_clkout[4]
to the transmitter data and control logic for all six channels.
Resetting or powering down channel 4 causes a loss of the clock for all six channels.
Note:
The common clock must have a 0 ppm difference for the read side of the transmitter phase compensation
FIFO of all the identical channels. A frequency difference causes the FIFO to under run or overflow, depending
on whether the common clock is slower or faster, respectively.
You can drive the 0 ppm common clock by one of the following sources:
•
tx_clkout
of any channel in non-bonded channel configurations
•
tx_clkout[0]
in bonded channel configurations
• Dedicated
refclk
pins
The Quartus II software does not allow gated clocks or clocks that are generated in the FPGA logic
to drive the
tx_coreclkin
ports.
Note:
You must ensure a 0 ppm difference. The Quartus II software is unable to ensure a 0 ppm difference because
it allows you to use external pins, such as dedicated
refclk
pins.
Transceiver Clocking in Cyclone V Devices
Altera Corporation
CV-53002
Selecting a Transmitter Datapath Interface Clock
2-24
2013.05.06