Visible to Intel only — GUID: bhc1460602022217
Ixiasoft
Visible to Intel only — GUID: bhc1460602022217
Ixiasoft
6.2.2. Advanced Clocking Mode Structure For Arria® 10, Cyclone® 10 GX, Stratix® V, and Arria® V Devices
Advanced clocking mode provides users the option to have different user interface clock frequency than the PHY core clock. Hence, there is PPM differences in this clocking mode. You must specify the user clock frequency through the Serial Lite III Streaming FPGA IP core parameter editor. Based on the user clock frequency value, the Quartus® Prime software automatically calculates the lane rate and core clock.
The parameter editor provides guidance in selecting a source user clock frequency that meets the transceiver data rate constraints. For more information about the lane rate calculation, refer to the “Transmission Overheads and Lane Rate Calculations” section.
set_instance_assignment -name GLOBAL_SIGNAL OFF -to *seriallite_iii_streaming*clock_gen:sink_clock_gen|dp_sync:coreclkin_reset_sync|dp_sync_regstage:dp_sync_stage_2*o*
The Serial Lite III Streaming Arria® 10 and Cyclone® 10 GX FPGA IP core uses the transmit serial clock bus (tx_serial_clk) and the tx_pll_locked signal to connect the external transmit PLL to the Transceiver Native PHY IP for Arria® 10 and Cyclone® 10 GX devices.
Clock Name | Description |
---|---|
Source | |
user_clock | User-defined. This clock is determined by the required throughput of the user application. For example, if the user interface is 384-bits wide (6 lanes × 64 bit/lane) and the required throughput is 120 Gbps, the user_clock frequency is 312.5 MHz. This clock is an input to the IP core and you should toggle this at the specified frequency. |
tx_serial_clk ( Arria® 10 and Cyclone® 10 GX devices) | This clock should toggle at one-half the data rate of the transceiver lane. When you enter the user_clock frequency in the IP parameter editor, the per lane data rate is calculated. Use that value and divided it by two to determine the tx_serial_clk. You are required to instantiate the TX PLL. An example of the TX PLL (ATX PLL) is generated with the IP core and is configured with the required reference clock and tx_serial_clk frequencies. |
interface_clock ( Stratix® V and Arria® V devices) | This is an internal clock and it is not exposed to the user. The frequency of this clock is derived from the transceiver data rate. It is lane data rate divided by 40. |
interface_clock | This is an internal clock and it is not exposed to the user. The frequency of this clock is derived from the transceiver data rate. The frequency is lane data rate divided by 64. |
Sink | |
xcvr_pll_ref_clk | This reference clock is used by the CDR unit in the transceiver. It serves as a reference for the CDR to be able to recover the clock from the serial line. The frequency of this clock must match the frequency you select in the IP parameter editor. It should also match the frequency of the tx_pll_ref_clk reference clock for the TX PLL at the Source variant. |
interface_clock | This clock is derived from the transceiver data. It is lane data rate divided by 64. It is an output of the IP core and should be used to clock the RX user application. |
Example of Implementing Specific User Interface Clock Frequency
An application requires the Serial Lite III Streaming IP core to sustain a frequency of 240 Gbps at the user interface.
user_clock (frequency) × number_of_lanes × 64 bits/lane = 240 Gbps
The data rate for Arria® 10 GX transceivers is limited to 17.4 Gbps. Therefore, 240 Gbps / 17.4 Gbps = 14 (rounding up)
Choosing 14 lanes gives:
user_clock (frequency) = 240 / (14 × 64) = 267.86 MHz
A value of 267.86 MHz is out of the supported range for the user_clock frequency. Therefore, you need to add one more lane.
user_clock (frequency) = 240 / (15 × 64) = 250 MHz
Choosing 250 MHz as the user_clock, the IP core provides the following values:
Transceiver data rate: 16.78 Gbps
interface_clk: 16.78 / 64 = 262.18 MHz
tx_serial_clock: 16.78 Gbps / 2 = 8390 MHz