Hello Tibor_Marko,
I hope all is great with you. Thank you for using the NXP communities.
Please review the response from our specialist below:
Keeping the NTM88 in continuous TX mode is done by using the MCU Direct Mode of the RF block. See section 10.16.1.2 of the user manual: https://www.nxp.com/webapp/Download?colCode=UM11227&appType=license
In Direct mode, the user application directly controls the RF output, and can therefore keep a continuous transmission.
I hope this information helps.
Regards,
David