Chapter 13

Software Drivers

Software drivers delivered with the Ethernet AVB Endpoint core provide the following functions, which utilize the dedicated hardware within the core for the Precise Timing Protocol (PTP) IEEE P802.1AS specification:

Best Clock Master Algorithm (BMCA) determines whether the core should operate in master clock or slave clock mode

PTP Clock Master functions

PTP Clock Slave functions that accurately synchronize the local Real Time Clock (RTC) to match that of the network clock master

The following definitions provide only a simplistic concept of PTP protocol operation. For detailed information about the PTP protocol, see the IEEE P802.1AS specification.

This chapter only describes the basic operation and some key components of the software drivers. The software driver code is documented such that the comments can be viewed by Doxygen and detailed descriptions of all aspects of the software are available throughout the code. This should allow customers to fully understand the operation of the provided software drivers and to edit the drivers for their own secret source applications.

Fundamentally, the slave “Real Time Clock” synchronization functions complete a software controlled phase-locked loop. Therefore, many implementations are possible. The provided software drivers implement a very simple software PLL implementation. However, this has been shown in hardware to provide excellent “Real Time Clock” synchronization results.

The document section “drivers/avb_v2_04_a/src” in Chapter 16 lists all of the C files delivered with the Ethernet AVB Endpoint core and provides a description of how the software is divided up between these files.

Clock Master

If the core is acting as clock master, the software drivers delivered with the core periodically sample the current value of the RTC and transmit this value to every device on the network using the P802.1 defined Sync and Follow-UpPTP packets.

Ethernet AVB Endpoint User Guide

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UG492 July 23, 2010

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Xilinx UG492 manual Software Drivers, Clock Master