2.5. Clocking Scheme
The clocking scheme illustrates the clock domains in the DisplayPort Intel® FPGA IP design example.
Figure 10. DisplayPort Intel® FPGA IP Design Example Clocking Scheme
| Clock | Signal Name in Design | Description | ||
|---|---|---|---|---|
| TX PLL Refclock | tx_pll_refclk | 135 MHz TX PLL reference clock, that is divisible by the transceiver for all DisplayPort data rates (1.62 Gbps, 2.7 Gbps, and 5.4 Gbps).
Note: The reference clock source of the TX PLL refclock is located at the HSSI refclk pin.
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| TX Transceiver Clockout | gxb_tx_clkout | TX clock recovered from the transceiver, and the frequency varies depending on the data rate and symbols per clock. |
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| Data Rate | Symbols per Clock | Frequency (MHz) | ||
| RBR (1.62 Gbps) |
2 (dual) |
81 | ||
| 4 (quad) | 40.5 | |||
| HBR (2.7 Gbps) |
2 (dual) | 135 | ||
| 4 (quad) | 67.5 | |||
| HBR2 (5.4 Gbps) |
2 (dual) | 270 | ||
| 4 (quad) | 135 | |||
| HBR3 (8.1 Gbps) |
4 (quad) | 202.5 | ||
| TX PLL Serial Clock | gxb_tx_bonding_clocks | Serial fast clock generated by TX PLL. The clock frequency is set based on the data rate. |
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| RX Refclock | rx_cdr_refclk | 135 MHz transceiver clock data recovery (CDR) reference clock, that is divisible by all DisplayPort data rates (1.62 Gbps, 2.7 Gbps, and 5.4 Gbps).
Note: The reference clock source of the RX refclock is located at the HSSI refclk pin.
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| RX Transceiver Clockout | gxb_rx_clkout | RX clock recovered from the transceiver, and the frequency varies depending on the data rate and symbols per clock. |
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| Data Rate | Symbols per Clock | Frequency (MHz) | ||
| RBR (1.62 Gbps) |
2 (dual) |
81 | ||
| 4 (quad) | 40.5 | |||
| HBR (2.7 Gbps) |
2 (dual) | 135 | ||
| 4 (quad) | 67.5 | |||
| HBR2 (5.4 Gbps) |
2 (dual) | 270 | ||
| 4 (quad) | 135 | |||
| HBR3 (8.1 Gbps) |
4 (quad) | 202.5 | ||
| Management Clock | rx_rcfg_mgmt_clk tx_rcfg_mgmt_clk |
A free running 100 MHz clock for both Avalon-MM interfaces for reconfiguration and PHY reset controller for transceiver reset sequence. |
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| Component | Required Frequency (MHz) | |||
| Avalon-MM reconfiguration | 100 – 125 | |||
| Transceiver PHY reset controller | 1 – 500 | |||
| Audio Clock | dp_audio_clk | DisplayPort audio clock. |
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| 16 MHz Clock | clk_16 | 160 MHz clock used to encode and decode auxiliary channel in the DisplayPort Intel® FPGA IP source and sink IP cores. This clock is also used as a reference clock in the Pixel Clock module for fractional calculation. |
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| Calibration Clock | dp_rx_clk_cal dp_tx_clk_cal |
A 50 MHz calibration clock input that must be synchronous to the Transceiver Reconfiguration module's clock. This clock is used in the DisplayPort Intel® FPGA IP core's reconfiguration logic. |
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| RX Video Clock | dp_rx_vid_clkout | Video clock for DisplayPort sink to clock video data stream. If MAX_LINK_RATE = HBR2 and PIXELS_PER_CLOCK = Dual, video clock uses 300 MHz. Otherwise, fixed to 160 MHz. |
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| TX Video Clock | tx_vid_clk | Recovered video clock from the PCR module that reflects the actual video clock frequency. Used when DisplayPort source's TX_SUPPORT_IM_ENABLE = 0. |
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| TX IM Clock | tx_im_clk | Video clock for DisplayPort source to clock video data stream. Must be the same as the RX video clock in this design. Used when DisplayPort source's TX_SUPPORT_IM_ENABLE = 1. |
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