Visible to Intel only — GUID: mcn1395909715016
Ixiasoft
Visible to Intel only — GUID: mcn1395909715016
Ixiasoft
2.3.14. PLL Reconfiguration
The PLLs use several divide counters and different VCO phase taps to perform frequency synthesis and phase shifts. In Intel® MAX® 10 PLLs, you can reconfigure both counter settings and phase shift the PLL output clock in real time. You can also change the charge pump and loop filter components, which dynamically affects the PLL bandwidth.
The following PLL components are configurable in real time:
- Pre-scale counter (N)
- Feedback counter (M)
- Post-scale output counters (C0-C4)
- Charge pump current (ICP)
- Loop filter components (R, C)
You can use these PLL components to update the following settings in real time without reconfiguring the entire FPGA:
- Output clock frequency
- PLL bandwidth
- Phase shift
The ability to reconfigure the PLL in real time is useful in applications that may operate in multiple frequencies. It is also useful in prototyping environments, allowing you to sweep PLL output frequencies and dynamically adjust the output clock phase.
For instance, a system generating test patterns is required to generate and send patterns at 75 or 150 MHz, depending on the requirements of the device under test. Reconfiguring the PLL components in real time allows you to switch between two such output frequencies in a few microseconds.
You can also use this feature to adjust clock-to-out (tCO) delays in real time by changing the PLL output clock phase shift. This approach eliminates the need to regenerate a configuration file with the new PLL settings.
The counter settings are updated synchronously to the clock frequency of the individual counters. Therefore, not all counters update simultaneously.
The dynamic reconfiguration scheme uses configuration files, such as the Hexadecimal-format file (.hex) or the Memory Initialization file (.mif). These files are used together with the Avalon ALTPLL RECONFIG Intel® FPGA IP to perform the dynamic reconfiguration.