CXD5602 User Manual
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863/1010
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3.9.15.11
INTERVAL Calculation Method
The INTERVAL is the value of “How many times data is input to the FIFO per the number of counts of the
32768 Hz counter”.
For example, the INTERVAL is 32768/64 = 512 when data sampled at 64 Hz is input as-is. The dimension is
“time” and the unit is 1/32768 (seconds).
The INTERVAL is used within the hardware for calculating the OLDEST_TIMESTAMP.
The following describes how to calculate the INTERVAL, which is necessary to obtain the
OLDEST_TIMESTAMP data by calculating.
LPADC
Obtains the values from the following related registers.
32 kHz frequency division setting of TOPREG: CKDIV_SCU.SCU_U32KL(@0x4E4+TOPREG region)
Channel select mode of SCU_ADCIF: LPADC_A1.LV_CH_SEL_MODE(@PWD_SCU region)
Set the SEL_DIV as follows according to the CH_SEL_MODE value (the intermediate parameter used here)
In the case of 4 (two channel mode)
SEL_DIV = 1
In the case of 5 (four channel mode)
SEL_DIV = 2
Other
SEL_DIV = 0
32 kHz frequency division setting register of SCU_ADCIF
LPADC_D1.SAMP_RATIO(@ PWD_SCU region)(for LPADC0)
LPADC_D4.SAMP_RATIO(@ PWD_SCU region)(for LPADC1)
LPADC_D5.SAMP_RATIO(@ PWD_SCU region)(for LPADC2)
LPADC_D6.SAMP_RATIO(@ PWD_SCU region)(for LPADC3)
Pick up the decimation ratio of CIC filter within MATH_PROC which is used
DECIMATION_PARAM0. N1 or N2 or N3(0x5084 PWD_SCU region)
or
DECIMATION_PARAM0. N4 or N5 or N6(0x5088 PWD_SCU region)
Set this to “0” when not using decimation.
/* get oldest timestamp from latest timestamp */
void GetOldestFromLatest (UH interval, UH uhAvail, UW *uwMsb, UH *uhLsb) {
UW tmpDiff;
UW tmpLsb;
if (uhAvail == 0) return;
tmpDiff = interval * uhAvail;
tmpLsb = (UW)(*uhLsb);
if (tmpLsb < tmpDiff) {
= 0x80000000;
tmpLsb -= tmpDiff;
(*uhLsb) = (UH)(tmpLsb & 0x00007fff);
(*uwMsb) = (*uwMsb) + (tmpLsb >> 15) - ((UW)(0x80000000) >> 15);
} else {
(*uhLsb) = (*uhLsb) - (UH)tmpDiff;
}
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