Intel IXP400 manual Ieee 1588 Hardware Assist Block, Overview

Intel® IXP400 Software

Access-Layer Components: Time Sync (IxTimeSyncAcc) API

synchronization, and internal processing delays. The slave element/node, after detecting the Sync or Follow_Up message, will begin the process to synchronize its system clock based on the master clock timestamp.

The slave may also initiate an synchronization request by sending a Delay_Req message with its local system time as the timestamp to the master. The master will then respond with Delay_Resp, carrying both the timestamp at which the Delay_Req was received and the timestamp included by the slave in the Delay_Req message. This allows the slave to determine the transit delay and accordingly to update its system time.

20.2.2IEEE 1588 Hardware Assist Block

Overview

The hardware provides necessary features to allow timestamping of the IEEE 1588 PTP messages. The IEEE 1588 Hardware Assist block internally snoops the MII interfaces that extend from the NPE components on the processor to Ethernet PHYs populated on the development or customer board. This provides the IEEE 1588 Hardware Assist block with the capability to detect the transversal of PTP protocol messages between the PHY and the MAC, and set internal timestamp registers with the appropriate data from these messages. When the timestamps of inbound or outbound messages are read by the hardware, the hardware block stores this information in a register.

The IEEE 1588 Hardware Assist block maintains a system time, which can be adjusted via API by the client application. Additionally, the block can be configured to interrupt the client application if the system time exceeds a specified target value.

Although IEEE 1588 PTP can be used for time synchronization of network elements/nodes over various communication media, this IEEE 1588 Hardware Assist block is designed to detect PTP messages over the NPE Ethernet interfaces only (not over the PCI interface).

Programmer’s Guide	IXP400 Software Version 2.0	April 2005
	Document Number: 252539, Revision: 007	285