Visible to Intel only — GUID: sfo1410068919296
Ixiasoft
Visible to Intel only — GUID: sfo1410068919296
Ixiasoft
18.2. EMAC Block Diagram and System Integration
The EMACs are integrated into the HPS portion of the system on a chip (SoC) device. They communicate with the I/O pins.
EMAC Overview
Each EMAC is an internal bus master that sends Ethernet packets to and from the System Interconnect. The EMAC uses a descriptor ring protocol, where the descriptor contains an address to a buffer to fetch or store the packet data.
Each EMAC has an MDIO Management port to send commands to the external PHY. Alternatively, you can use an I2C module in the HPS for the management interface.
Each EMAC has an IEEE 1588 Timestamp interface with 20 ns resolution. The Arm* Cortex®-A9 microprocessor unit (MPU) subsystem can use it to maintain synchronization between the time counters that are internal to the three MACs. The clock reference for the timestamp can be provided by the Clock Manager (emac_ptp_clk) or the FPGA fabric (f2s_emac_ptp_ref_clk). The clock reference is selected by the ptp_clk_sel bit in the emac_global register in the system manager.