External Memory Interface Handbook Volume 3: Reference Material

ID 683841
Date 7/24/2019
Public
Document Table of Contents

1.3. Dedicated Clock Networks

The UniPHY layer employs three types of dedicated clock networks:
  • Global clock network
  • Dual-regional clock network
  • PHY clock network (applicable to Arria V, Cyclone V, and Stratix V devices, and later)

The PHY clock network is a dedicated high-speed, low-skew, balanced clock tree designed for high-performance external memory interface. For device families that support the PHY clock network, UniPHY always uses the PHY clock network for all clocks at the PHY-memory boundary.

For families that do not support the PHY clock network, UniPHY uses either dual-regional or global clock networks for clocks at the PHY-memory boundary. During generation, the system selects dual-regional or global clocks automatically, depending on whether a given interface spans more than one quadrant. UniPHY does not mix the usage of dual-regional and global clock networks for clocks at the PHY-memory boundary; this ensures that timing characteristics of the various output paths are as similar as possible.

The <variation_name>_pin_assignments.tcl script creates the appropriate clock network type assignment. The use of the PHY clock network is specified directly in the RTL code, and does not require an assignment.

The UniPHY uses an active-low, asychronous assert and synchronous de-assert reset scheme. The global reset signal resets the PLL in the PHY and the rest of the system is held in reset until after the PLL is locked.

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