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Functional Description
• Write the rftclk_sel[4:0] value in the RFTCLK_Sel register with the desired reference clock multiplexor
value. This value is allowed to be written only when the cpts_en bit is cleared to zero.
• Write a one to the cpts_en bit in the TS_Control register. The RCLK domain is in reset while this bit is
low.
• Enable the interrupt by writing a one to the ts_pend_en bit in the TS_Int_Enable register (if using
interrupts and not polling).
14.3.7.2.2 Time Stamp Value
The time stamp value is a 32-bit value that increments on each RCLK rising edge when CPTS_EN is set
to one. When CPTS_EN is cleared to zero the time stamp value is reset to zero. If more than 32-bits of
time stamp are required by the application, the host software must maintain the necessary number of
upper bits. The upper time stamp value should be incremented by the host when the rollover event is
detected.
For test purposes, the time stamp can be written via the time stamp load function (CPTS_LOAD_VAL and
CPTS_LOAD_EN registers).
14.3.7.2.3 Event FIFO
All time sync events are pushed onto the Event FIFO. There are 16 locations in the event FIFO with no
overrun indication supported. Software must service the event FIFO in a timely manner to prevent FIFO
overrun.
14.3.7.2.4 Time Sync Events
Time Sync events are 64-bit values that are pushed onto the event FIFO and read in two 32-bit reads.
CPTS_EVENT_LOW and CPTS_EVENT_HIGH are defined in Section 14.5.3.10 and Section 14.5.3.11,
respectively.
There are six types of sync events
• Time stamp push event
• Hardware time stamp push event
• Time stamp counter rollover event
• Time stamp counter half-rollover event
• Ethernet receive event
• Ethernet transmit event
14.3.7.2.4.1 Time Stamp Push Event
Software can obtain the current time stamp value (at the time of the write) by initiating a time stamp push
event. The push event is initiated by setting the TS_PUSH bit of the CPTS_TS_PUSH register. The time
stamp value is returned in the event, along with a time stamp push event code. Software should not push
a second time stamp event on to the FIFO until the first time stamp value has been read from the event
FIFO.
14.3.7.2.4.2 Time Stamp Counter Rollover Event
The CPTS module contains a 32-bit time stamp value. The counter upper bits are maintained by host
software. The rollover event indicates to software that the time stamp counter has rolled over from
0xFFFF_FFFF to 0x0000_0000, and the software maintained upper count value should be incremented.
1229
SPRUH73H–October 2011–Revised April 2013 Ethernet Subsystem
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