wonderfuliot:
Did you mean 'RegModemStat', bit 'RX on-going' ?
The 'RX on-going' bit in RegModemStat register does not give the status of a pkt rx in progress.
This bit is only an indicator for modem RX Mode. Misleading name in the datasheet.
In fact there are various bits toggling across in that register while the pkt is being received but there is no single bit that gives out that status 