Chapter 8: Real Time Clock And Time Stamping; Real Time Clock - Xilinx LogiCORE IP Ethernet AVB Endpoint v2.4 User Manual

Real Time Clock and Time Stamping
This chapter considers two of the logical components that are partially responsible for the
AVB timing synchronization protocol.
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These are both described in this chapter as they are closely related.

Real Time Clock

A significant component of the PTP network wide timing synchronization mechanism is
the Real Time Counter (RTC), which provides the common time of the network. Every
device on the network will maintain its own local version.
The RTC is effectively a large counter which consists of a 32-bit nanoseconds field (the unit
of this field is 1 nanosecond and this field will count the duration of exactly one second,
then reset back to zero) and a 48-bit seconds field (the unit of this field is one second: this
field will increment when the nanosecond field saturates at 1 second). The seconds field
only wraps around when its count fully saturates. The entire RTC is therefore designed
never to wrap around in our lifetime. The RTC is summarized in
X-Ref Target - Figure 8-1
Seconds field (48 bits unsigned)
counts from 0 until fully saturated,
then wraps around to 0
Ethernet AVB Endpoint User Guide
UG492 September 21, 2010
"Real Time Clock"
"Time Stamping Logic"
IEEE802.1AS Real Time Counter (RTC)
Figure 8-1: Real Time Counter (RTC)
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Chapter 8
Figure 8-1.
Nano Seconds field (32 bits unsigned)
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counts from 0 to 1 x 10 -1,
then resets to 0
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