Xilinx IP Ethernet AVB Endpoint v2.4 UG492 Manual de usuario descargar pdf (Pagina 77)

Ethernet AVB Endpoint User Guide www.xilinx.com 77

UG492 September 21, 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

1 2 ... 72 73 74 75 76 77 78 79 80 81 82 ... 171 172

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Xilinx IP Ethernet AVB Endpoint v2.4 UG492 Manual de usuario Pagina 77