Visible to Intel only — GUID: bhc1410937212102
Ixiasoft
Visible to Intel only — GUID: bhc1410937212102
Ixiasoft
5.4.5. Dynamic TX Clock Switching for Arria V, Cyclone V, and Stratix V Devices
The dynamic TX clock switching feature allows you to dynamically switch between NTSC and PAL transceiver data rates for all video standards except SD-SDI.
- Instantiate an alternate TX PLL and supply two different clocks to the two PLLs. Switch between the primary PLL and the alternate PLL for transmission.
- Use the primary PLL with two reference input clocks. The PLL switches between these two clocks for transmission.
To implement this feature, you are required to provide two reference clocks (xcvr_refclk and xcvr_refclk_alt) to the SDI II IP core. The frequency of the reference clocks must be assigned to 148.5 MHz and 148.35 MHz in any assignment order.
- Set ch1_{tx/du}_tx_pll_sel to 0 to select xcvr_refclk
- Set ch1_{tx/du}_tx_pll_sel to 1 to select xcvr_refclk_alt
To complete the handshaking process, you must deassert the reconfiguration request signal (ch1_{tx/du}_tx_start_reconfig) upon assertion of the reconfiguration done signal (ch1_{tx/du}_tx_reconfig_done). The dynamic TX clock switching only takes effect after the tx_rst is asserted high and deasserted low accordingly.
The table below describes the behavior of the dynamic switching feature when you initiate a handshaking process (with reference to the timing diagram).
Case | Description |
---|---|
1 | The handshaking process attempts to switch to select xcvr_refclk_alt. tx_clkout successfully locks to xcvr_refclk_alt (148.35 MHz). |
2 | The handshaking process attempts to switch to select xcvr_refclk. tx_clkout successfully locks to xcvr_refclk (148.5 MHz). |
3 | The handshaking process attempts to switch to select xcvr_refclk_alt. The switching fails because ch1_{tx/du}_tx_pll_sel changes from 1 to 0 before the assertion of ch1_{tx/du}_tx_start_reconfig. Therefore, tx_clkout remains locked to xcvr_refclk (148.5MHz). |
Implementing TX PLL and Reference Clock Switching
- Trigger the tx_pll_sel signal to the desired reference clock: 0 for 148.5 or 1 for 148.35 MHz.
- Assert the tx_start_reconfig signal at the same clock cycle. You may assert the signal at the next clock cycle as long as you do not toggle back the tx_pll_sel signal.
- Keep the tx_start_reconfig signal asserted until the tx_reconfig_done signal asserts.
- Deassert the tx_start_reconfig signal and assert the tx_rst signal at the next cycle.
- The TX clock (tx_clk) should run at the new frequency now.