Article ID: 000075481 Content Type: Troubleshooting Last Reviewed: 04/06/2023

Can I enable multiple controllers clock sharing in ALTMEMPHY-based High-Performance Memory Controller for Cyclone® III and Cyclone® IV device?



Multiple controllers clock sharing option allows the controllers to share the static PHY clocks between multiple controllers that run on the same frequency and must share the same phase-locked loop (PLL) reference clock.

However, there is a limitation if you would like to enable this feature on Cyclone® III and Cyclone IV device family.

  1. For design with two ALTMEMPHY instances, two PLLs will still be utilized.
    This is explained in the following knowlegde article:
    Can I share a single PLL for two ALTMEMPHY instances in my design?
  2. For ALTMEMPHY-based memory controller, PLL should be fed on its fully compensated dedicated input pin to reduce Jitter and this is one of the timing model assumptions for PLL and clock network.

    "The reference input clock signal to the PLL must be driven by the dedicated clock input pin located adjacent to the PLL, or from the clock output signal from the adjacent PLL. To minimize output clock jitter, the reference input clock pin to the ALTMEMPHY PLL must not be routed through the core using global or regional clock networks."
  3. Cyclone III and Cyclone IV devices do not have fully compensated dedicated clock input that could feed two PLLs.

Such PLL clock network is only available on Arria® II GX, Stratix® III, and Stratix® IV device family.

Arria II GX device
- CLK[8..11] for PLL_5 and PLL_6

Stratix III, Stratix IV device
- CLK[0..3] for PLL_L2 and PLL_L3
- CLK[4..7] for PLL_B1 and PLL_B2
- CLK[8..11] for PLL_R2 and PLL_R3
- CLK[12..15] for PLL_T1 and PLL_T2

For these reasons, multiple controllers clock sharing should not be used on Cyclone III and Cyclone IV device family.



Consider having separate clock input for each memory controllers on Cyclone III and Cyclone IV device.

Related Products

This article applies to 3 products

Cyclone® III FPGAs
Cyclone® IV FPGAs
Cyclone® IV E FPGA