The hardware always aligns the first IQ sample in the first sample slot.
The duration between the first sample of the reference period and the first sample of the first sample slot is independent from TSAMPLESPACINGREF. However, as a consequence, the duration between the last sample in the reference period and the first sample in the first sample slot is not independent from TSAMPLESPACINGREF. The following diagram illustrates this behavior.
Figure 1. First sample slot
