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56 www.xilinx.com Ethernet AVB Endpoint User Guide
UG492 July 23, 2010
Chapter 5: Core Architecture
PTP Signals
Table 5-11 defines the signals which are output from the core by the “Precise Timing
Protocol Blocks.” These signals are provided for reference only and may be used by an
application. For example, the 1722 Packet Managers, as illustrated in Figure 3-2, require
the following:
• clk8k: this marks the class measurement interval to be used for traffic shaping for SR
class A AV traffic.
• rtc_nanosec_field and rtc_sec_field: used in the 1722 presentation time
stamp logic.
Table 5-11: PTP Signals
Signal Direction Description
rtc_nanosec_field[31:0] Output This is the synchronized nanoseconds field
from the “RTC.”
rtc_sec_field[47:0] Output This is the synchronized seconds field
from the “RTC.”
clk8k Output This is an 8KHz clock which is derived
from, and synchronized in frequency, to
the “RTC.”
rtc_nanosec_field_1722[31:0] Output The IEEE1722 specification contains a
different format for the “RTC,”provided
here as an extra port. This is derived and is
in sync with the IEEE802.1 AS RTC. If
desired, this port can be used as the RTC
reference for 1722 Packet Manager blocks,
as illustrated in
Figure 3-2. See also
“IEEE1722 Real Time Clock Format,”
page 81.