Intel IXP400 manual IxTimeSyncAcc API Details, Ieee 1588 PTP Client Application

Intel® IXP400 Software

Access-Layer Components: Time Sync (IxTimeSyncAcc) API

VLAN-tagged Ethernet frames include an additional four bytes prior to the beginning of the original Ethernet Type/Length field. The IP header immediately follows the Type/Length field. VLAN-tagged Ethernet frames can be identified by the value of 0x8100 at offset 12 and 13 of the Ethernet frame. If the IEEE 1588 Hardware Assist block identifies a value of 0x8100 (i.e., VLAN TPID field) at this offset, it will adjust the offsets it uses to support PTP messages by four bytes.

Note: Some popular Ethernet switch PHY chips use the same bytes in VLAN-tagged frames to encode the port through which a frame is received. These devices encode the physical port from which a frame is received in the least-significant four bits of offset 13. The IEEE 1588 Hardware Assist block will be unable to detect Sync and Delay_Req messages in this scenario.

Additional Hardware Information

For more information on the IEEE 1588 Hardware Assist block, please refer to the Intel hardware documentation for the Intel® IXP46X Product Line.

20.2.3IxTimeSyncAcc

The IxTimeSyncAcc access-layer component provides a software interface to configure the IEEE 1588 Hardware Assist block, and provide access to the snapshot register data. More details are provided in “IxTimeSyncAcc API Details” on page 288.

20.2.4IEEE 1588 PTP Client Application

A IEEE 1588 PTP client application is application code running on the Intel XScale core that utilizes the IxTimeSyncAcc API (and other APIs in the IXP400 software) to implement and use PTP messages and timestamps according to the IEEE 1588 specifications.

The IXP400 software does not provide this client application, although it does include a codelet that demonstrates the basic usage of the APIs in some IEEE 1588 scenarios. Refer to Chapter 23.

A common scenario would involve a IEEE 1588 client application implementing a slave, master, or boundary clock on the target hardware platform. When transmitting PTP protocol messages, the client application would need to obtain the appropriate timestamp information from IxTimeSyncAcc, construct the appropriate PTP protocol messages, and transmit the messages using the Ethernet subsystem of the IXP400 software. When receiving PTP protocol messages, the client application may poll via the IxTimeSyncAcc API for the existence of new timestamp and other related PTP message information. If the remainder of the PTP message content is of interest to the client application, it will need to receive the Ethernet frame via the Ethernet subsystem of the IXP400 software (i.e., IxEthAcc).

When operating over Ethernet networks, these messages are carried in frames using the UDP transport-layer. UDP does not guarantee successful message transfer between sending and receiving nodes, and the IEEE 1588 client application must take this behavior into account.

20.3IxTimeSyncAcc API Details

20.3.1Features

IxTimeSyncAcc API provides the following features:

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