The RDS information is classified into different frame types. Different frame types are sent at different frequencies, eg: the PI is sent much more frequently (25%) than a PTY. Here we give a description of some frame types that are needed and how to assemble these frames into a block ready for encoding into the symbol stream for transmission.
Full information on the frames types can be found in the standards documantation and is beyond the scope of this web site. here we will deal with some the frames where relevent to understanding how the various frame types and repetion rate of the frames determines how the frames are assembled into a super frame or Block. Once so assembled the information we want to transmit a symbol list is generated and sent to the RISC engine. The RISC engine then programs the DAC to generate the RDS waveform. Once sent the symbol information is sent to the RISC engine, the transmission is repeated ad-infintum until such time a new symbol list is created.
The RDS data is divided into 16 frames types in format A or B. Each frame has 104bits, divided into 4 equal sections of 26 bits. Each of these 26 bit sections are spli into a 16 bit information word and 10 bit checkword. The check word is for error correction and synchronisation.
The content of each information word varies as to the frame type and is different for each of the 4 information words per frame type.
The RDS standard defines a recomended repetition rate for the different types of RDS frames. This requirement sets the length of the super frame/block we use.