Sony CXD5602 User Manual page 862

3.9.15.9 OLDEST Time Stamp Restriction
The OLDEST time stamp calculated by the hardware has the following restrictions. These restrictions can be
avoided by using the LATEST time stamp.
・When FORCE_THROUGH within the SCU_REG is set to "1" at the Decimation partition, the decimation ratio
must be calculated using "1" but when the decimation ratio of the CIC filter is nine or smaller, that value is used.
・When the XOSC is used at the HPADC, and the sampling frequency is not a power of 2, the time stamp cannot
be accurately calculated. This is because the corresponding arithmetic circuit within the hardware is comprised of
a bit shift circuit.
・If the One-shot Operation is performed by the sequencer with the same ID as ID assigned for the ADC readout,
the time stamp of the ADC will be incorrect. This is because 0xA must be set in the START_INTERVALn field
of the START_INTERVAL register within the SCU_REG when using the One-shot Sequencer.
3.9.15.10 Converting the LATEST Time Stamp to the OLDEST Time Stamp
The LATEST_TIMESTAMP can be converted to the OLDEST_TIMESTAMP.
Due to the restrictions of the OLDEST_TIMESTAMP (refer to Section 3.9.15.9), there are cases where you will
need to convert the LATEST_TIMESTAMP to the OLDEST_TIMESTAMP.
This can be done by the following equation.
OLDEST_TIMESTAMP = LATEST_TIMESTAMP - INTERVAL x remaining FIFOs
(For the LATEST_TIMESTAMP and the remaining number of data, the ones read out after data transfer are used.
In the case that readout is performed before the transfer, errors will occur due to writing data during the
subsequent data readouts.)
The calculation for INTERVAL will be described later.
The following is an example of pseudo code for LATEST to OLDEST conversion.
－862/1010－
CXD5602 User Manual