Xilinx IP Ethernet AVB Endpoint v2.4 UG492 - Manual (Page 132)

132 www.xilinx.com Ethernet AVB Endpoint User Guide
UG492 September 21, 2010
Chapter 13: Software Drivers
Clock Slave
If the core is acting as a clock slave, the local RTC is closely matched to the value and
frequency of the network clock master. This is achieved, in part, by receiving the PTP Sync
and Follow-Up frames transmitted across the network by the clock master (and containing
the sampled RTC value of the master). The PTP mechanism also tracks the total routing
delay across the network between the clock master and itself. The software drivers use this
data, in conjunction with recent historical data, to calculate the error between its local RTC
counter and that of the RTC clock master. The software then periodically calculates an RTC
correction value and an updated increment rate, and these values are written to
appropriate RTC configuration registers.
Because the drivers are provided as C code text files, they can be easily modified and
designers can edit the files to provide their own secret source, or even to update the
software drivers for P802.1AS specification changes.
Software System Integration
The software drivers for the Ethernet AVB Endpoint core need to be run on an embedded
processor. In addition, they require instantiation into the overall software project, and then
initialization.
An example software project file that performs the required steps is included with the core
in the following location:
<component_name>/MyProcessorIPLib/drivers/
ethernet_avb_endpoint_v2_04_a/examples/xavb_example.c
This software example has been tested in a real system. For this reason, use this file for
reference, along with the following descriptions:
•
“Driver Instantiation”
• “Interrupt Service Routine Connections”
• “Core Initialization”
• “Ethernet AVB Endpoint Setup”
• “Starting and Stopping the AVB Drivers”
Note: Unless you are already familiar with the Xilinx Embedded Development Kit (EDK), see the
EDK documentation to follow the steps described.
Driver Instantiation
Software driver instantiation for the Ethernet AVB Endpoint core follows the standard
EDK model used for all EDK IP cores and as recommended for all user defined pcores (see
the
EDK documentation ). Initialization of the driver requires that an instance of the driver
is instantiated, assigned a base address within the PLB address range, and configured
using the standardized cores
CfgInitialize function.