Visible to Intel only — GUID: oxp1603918707658
Ixiasoft
Visible to Intel only — GUID: oxp1603918707658
Ixiasoft
2.4.1.1. FHT Reference Clock Network
There are two reference clocks (refclk[0] and refclk[1]) for FHT PMAs, both accessible by any of the four FHT PMAs. refclk[0] and refclk[1] can be different frequencies. The frequency range is 100-200 MHz, and it is a continuous range.
As shown in FHT Reference Clock Network, FHT has six PLLs.
- Two common PLLs connected to all four lanes: PLL A and PLL B
- Four lane PLLs, one PLL per lane for all four lanes: TX PLL
To optimize performance, FHT has a cascaded PLL scheme between common PLLs and lane PLLs, the common PLLs providing a cleaner clock to the lane PLLs.
- Common PLLs and lane PLLs support integer and fractional modes. However, a common PLL cannot be in fractional mode when the corresponding lane PLL is in fractional mode. See the following table.
- One common PLL drives the microcontroller. The reference clock that drives this common PLL must be present and stable throughout F-tile operation.
- Common PLLs generate two clock frequencies (100 and 156.25 MHz) which go to the lane PLLs. One of them must be selected to drive the lane PLLs.
Lane PLL Mode | Corresponding Common PLL Mode | Supported or Not Supported |
---|---|---|
Integer | Integer | Supported |
Integer | Fractional | Supported |
Fractional | Integer | Supported |
Fractional | Fractional | Not supported |
FHT Reference Clocks | Direction | Accessible FHT PMA | Accessible to System PLLs? |
---|---|---|---|
refclk[0] | Input | FHT0, FHT1, FHT2, FHT3 | No |
refclk[1] | Input | FHT0, FHT1, FHT2, FHT3 | No |