CCS/CC2652P: Question about timestamp, timestamp2 and RF_getCurrentTime()

Thank you.

My application is 2.4GHz and the data rate is 250kbps, but I found something strange.

I output some debug information about timestamp via uart in dataCnfCb as below:

09:19:28:971-<

tx ts : 232736, tx ts2 : 43, tx rf : 14901254

09:21:41:751-<

tx ts : 8532603, tx ts2 : 61, tx rf : 546092550

This output information is in dataCnfCb. “tx ts” is timestamp, “tx tx2” is timestamp2, tx rf is RF_getCurrentTime().

According to this equation 

timestamp2 = txTime % (timer ticks per symbol).

So, timestamp2 will always be smaller than timer ticks per symbol.

But, in my output information, timestamp2 is 43 and 61.

I have made dozens of tests, the maximum timestamp2 I observed is 63 and the minimum timestamp2 I observed is 1.

So use 16 as timer ticks per symbol seems not reasonable, and 64 seems more reasonable.

So, could you please help me with this?

Can you provide the exact code examples and modifications made to make these observations?

Regards,
Ryan

Here is my code :

static void dataCnfCB(ApiMac_mcpsDataCnf_t *pDataCnf)
{
    uint32_t tx_ts, tx_rf;
    uint16_t tx_ts2;
    tx_rf = RF_getCurrentTime();
    tx_ts = pDataCnf->timestamp;
    tx_ts2 = pDataCnf->timestamp2;

    printf("tx ts : %u, tx ts2 : %u, tx rf : %u\n", tx_ts, tx_ts2, tx_rf);
}

 Here is my syscfg:

In this project, I observed that timestamp2 in dataCnfCb can be up to 63. Here are some examples:

tx ts : 1174572, tx ts2 : 53, tx rf : 75189304

tx ts : 1289556, tx ts2 : 24, tx rf : 82547641

tx ts : 1602493, tx ts2 : 45, tx rf : 102576223

And, I looked up this document:

There is a table in this document as below

For 2.4GHz, 250kbps, the symbol rate is 62.5ksymbol/s. So, one symbol is 1/62.5 s=1000000/62.5 us = 16us.

So timer ticks per symbol is 16us/0.25us = 64.

Is that right?