Before RADIO can transmit a packet, it must first ramp-up in TX mode. See TXRU in Radio states and Transmit sequence. A TXRU ramp-up sequence is initiated when the TXEN task is triggered. After RADIO has successfully ramped up it will generate the READY event indicating that a packet transmission can be initiated. A packet transmission is initiated by triggering the START task. The START task can first be triggered after RADIO has entered into the TXIDLE state.
The following figure illustrates a single packet transmission where the CPU manually triggers
the different tasks needed to control the flow of RADIO, i.e. no shortcuts are used. If
shortcuts are not used, a certain amount of delay caused by CPU execution is expected between
READY and START,
and between END and DISABLE. As illustrated in the following figure, RADIO will by default transmit
1s between READY and START, and between END
and DISABLED. What is transmitted can be programmed
through the DTX field in the MODECNF0 register.
The following figure shows a slightly modified version of the transmit sequence where RADIO is configured to use shortcuts between READY and START, and between END and DISABLE, which means that no delay is introduced.
RADIO is able to send multiple packets one after the other without having to disable and re-enable RADIO between packets, as illustrated in the following figure.