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, meaning 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 PHYEND and DISABLE. As illustrated in the following figure, RADIO will by default transmit an unmodulated carrier between READY and START, and between PHYEND and DISABLED.
The following figure shows a transmit sequence where no delay is introduced. RADIO is configured to use shortcuts between READY and START, and between PHYEND and DISABLE.
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.