Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 11/27/2024
Public
Document Table of Contents

5.1.7. EMAC Programming Model

The initialization and configuration of the EMAC and its interface is a multi-step process that includes system register programming in the system manager and clock manager and configuration of clocks in multiple domains.
Note: When the EMAC interfaces to HPS I/O and register content is being transferred to a different clock domain after a write operation, no further writes should occur to the same location until the first write is updated. Otherwise, the second write operation does not get updated to the destination clock domain. Thus, the delay between two writes to the same register location should be at least four cycles of the destination clock (PHY receive clock, PHY transmit clock, or PTP clock). If the CSR is accessed multiple times quickly, you must ensure that a minimum number of destination clock cycles have occurred between accesses.
Note: If the EMAC signals are routed through the FPGA fabric and it is assumed that the transmit clock supplied by the FPGA fabric switches within six transmit clock cycles, then the minimum time required between two write accesses to the same register is ten transmit clock cycles.