FMUSER INTERNATIONAL GROUP INC.
广州市汉婷生物技术开发有限公司
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14.2 RDS Group Format
Following information is provided for better understanding to the RDS principles and the user defined group coding.
The largest element in the RDS coding structure is called a "group" of 104 bits each. Each group comprises 4 blocks
of 26 bits each. Each block comprises an information word and a checkword. Each information word comprises 16
bits. Each checkword comprises 10 bits.
All information words, checkwords, binary numbers or binary address values have their most significant bit (MSB)
transmitted first.
The data transmission is fully synchronous and there are no gaps between the groups or blocks. The basic data-
rate of the system is 1187.5 bit/s. Thus transmission of one group takes about 87.6 ms and about 11.4 groups are
transmitted per one second.
General RDS group format.
14.2.1 Basic principles and rules
The services which are to be repeated most frequently, and for which a short acquisition time is required (PI, TP,
PTY), in general occupy the same fixed positions within every group.
There is no fixed rhythm of repetition of the various types of group, i.e. there is ample flexibility to interleave the
various kinds of message to suit the needs of the users at any given time.
The first four bits of the second block of every group are allocated to a four-bit code which specifies the
application of the group - group type. Groups are referred to as types 0 to 15.
For each type (0 to 15) two "versions" can be defined. The "version" is specified by the fifth bit of block 2: 0
= version A, 1 = version B.
For all groups of version B the PI is inserted also in block 3 so this block cannot carry any other information when
version B of the group is used.
14.2.2 Remarks
One complete PS label consists of 4 groups. So one PS takes 350 ms of the transmission time. It may be found
from experience that any RDS text should be transmitted at least twice to improve reception reliability. With regard
to other services included in the RDS the repetition rate of dynamic/scrolling PS usually cannot be lower than one
second.
Checkwords and offsets are always computed and inserted automatically by the RDS encoder.
PI is always inserted automatically by the RDS encoder in block 1, and also in block 3 for version B of the group.
Due to this the block 1 is never specified when inserting any user defined group.
TP and PTY are always inserted automatically by the RDS encoder using OR method (logical sum) on
the appropriate bit positions.
