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Ethernet AVB Endpoint User Guide www.xilinx.com 77

UG492 July 23, 2010

Real Time Clock

RTC Implementation

Increment of Nanoseconds Field

Figure 8-2 illustrates the implementation used to create the RTC nanoseconds field. This is

performed by the use of an implementation specific 20-bit sub-nanoseconds field as

illustrated. The nanoseconds and sub-nanoseconds fields can be considered to be

concatenated together.

All RTC logic within the core is synchronous to the RTC Reference Clock, rtc_clk.

X-Ref Target - Figure 8-2

Figure 8-2: Increment of Sub-nanoseconds and Nanoseconds Field

Nano Seconds (32 bits unsigned) Sub-Nano Seconds

(20 bits unsigned)

RTC Increment Value (26 bits)

(written by processor)

fill with zero’s

RTC Nano Seconds Offset (30 bits)

(written by processor)

Step 1

Step 2

controlled frequency RTC

Synchronised RTC

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Xilinx UG492 Bedienungsanleitung Seite 77