AN243,AN243 pdf中文资料,AN243引脚图,AN243电路-Datasheet-电子工程世界

Datasheet> 器件分类 > AN243

文档预览

AN243: 产品描述Describe the high-level differences between RDS and RBDS; 文件大小1MB，共16页; 制造商SILABS; 官网地址http://www.silabs.com

下载文档全文预览

AN243概述

Describe the high-level differences between RDS and RBDS

文档预览

下载PDF文档

全文
预览

AN243

S I NG

RDS/RBDS

WITH THE

Si4701/03

1. Scope

This document applies to the Si4701/03 firmware revision 15 and greater. Throughout this document, device refers

to an Si4701 or Si4703.

2. Purpose



Provide an overview of RDS/RBDS

Describe the high-level differences between RDS and RBDS

Show the procedure for reading RDS/RBDS data from the Si4701

Show the procedure for post-processing of RDS/RBDS data

Point the reader to additional documentation

3. Additional Documentation

[1] The Broadcaster's Guide to RDS, Scott Wright, Focal Press, 1997.

[2] CENELEC (1998): Specification of the radio data system (RDS) for VHF/FM sound broadcasting.

EN50067:1998. European Committee for Electrotechnical Standardization. Brussels Belgium.

[3] National Radio Systems Committee: United States RBDS Standard, April 9, 1998 - Specification of the radio

broadcast data system (RBDS), Washington D.C.

[4] Si4701-B15 Data Sheet

[5] Si4703-B16 Data Sheet

[6] Application Note “AN230: Si4700/01/02/03 Programming Guide”

[7] Traffic and Traveller Information (TTI)—TTI messages via traffic message coding

(ISO 14819-1) Part 1: Coding protocol for Radio Data System—Traffic Message Channel (RDS-TMC) using ALERT-C

(ISO 14819-2) Part 2: Event and information codes for Radio Data System—Traffic Message Channel (RDS-TMC)

(ISO 14819-3) Part 3: Location referencing for ALERT-C

(ISO 14819-6) Part 6: Encryption and conditional access for the Radio Data System—

Traffic Message Channel ALERT C coding

[8] Radiotext plus (RTplus) Specification

4. RDS/RBDS Overview

The Radio Data System (RDS*) has been in existence since the 1980s in Europe, and since the early 1990s in

North America as the Radio Broadcast Data System (RBDS). In 1998, the US and Europe spurred RDS adoption

rates by largely unifying the existing RDS and RBDS standards.

Since the 1998 unifying amendments, RDS has gained substantial market adoption in the US, Europe, and other

countries worldwide. It is standard in vehicles and radio equipment from many leading manufacturers. The cost to

enable a broadcast station with RDS can be less than $500, and many North and South American, European, and

Asian radio stations broadcast with some RDS capability. And with extremely small, power-efficient RDS solutions

such as the Si4701/03, RDS is making in-roads in many millions of portable devices such as handsets, portable

radios, and portable music/media players.

RDS is an auxiliary signal to the FM broadcast system. As it is auxiliary, the modulated signal must not degrade the

primary audio signal, and so RDS is typically only decipherable on strong broadcasts. Figure 1 depicts the FM

broadcast components. At the far left of the graphic the mono signal is broadcast with the greatest strength or

deviation in kHz along the y-axis. This means that a signal will first be received and output in mono until the FM

signal is clear enough for the FM receiver to demodulate the stereo signals. RDS is broadcast with the least

Rev. 0.2 3/07

AN243

AN243

deviation, limited to 7.5 kHz in the standard, but typically broadcast at about 2 kHz; therefore, RDS is generally

difficult for the receiver to decode unless a signal is fairly strong. In urban environments with many large

broadcasting stations, an FM tuner with modest performance can typically receive many signals which exceed the

requirements for decoding RDS.

*Note:

RDS/RBDS will be noted as only RDS throughout this paper since the two standards are largely unified.

Modulation Level

Mono Audio

Left + Right

Stereo

Pilot

Stereo Audio

Left - Right

RDS/

RBDS

15 19 23

Frequency (kHz)

Figure 1. MPX Signal Spectrum

RDS in Europe and RBDS in North America are identical at the physical layer, and nearly identical at the data-link

and presentation layers, with exceptions highlighted in Section 7. Differences between the data-link layers are

managed internally by the device. Key differences at the presentation layer are discussed later in this document.

The remainder of this document refers to RDS and RBDS simply as RDS where a distinction is not required.

RDS is transmitted in a continuous stream of four data blocks each containing 26 bits of content and error-

correction information. Each set of four blocks constitutes a group. There are required repetition rates in the

standard to which all RDS-certified transmitting devices must adhere (shown in Table 2), but aside from this, all

information related to presenting the content of an RDS group is contained within the four blocks of data.

Figure 2. Structure of the Baseband Coding

The blocks each contain 26 bits; 16 bits in the information word, and 10 bits in the checkword and offset word. The

checkword and offset word contain error correction, synchronization, and block identification information. The

information word contains the coded content of the data blocks including RDS group types and associated content,

and represents 64 total bits per group of four data blocks (16 x 4 = 64).

There are 32 possible group types ranging from basic tuning information and emergency warnings, to "Open Data

Applications (ODA)" which can support many content types. In most of the North American and European markets,

only a few RDS groups are used by the broadcasters conveying station identifiers, alternative frequencies between

broadcast coverage areas, traffic alerts and locations, and relevant information to the broadcast content. Other

markets are currently using similar group patterns.

The information coded into each RDS group has a common fixed structure according to the RDS group type. The

structure dictates a standard repetitive data format and repetition rate to maximize reliability in all environments,

while allowing for content flexibility. The structure for all RDS group types is shown in Figure 3.

Rev. 0.2

AN243

Figure 3. Message Format and Addressing

Figure Notes:

PI code = Program Identification code = 16 bits (see Section 3.2.1.1 and annex D of the RBDS Standard)

Checkword + offset "N" = 10 bits added to provide error protection and block and group synchronization information (see

Sections 2.3 and 2.4 and annexes A, B and C of the RBDS Standard)

Group type code = 4 bits A[3:0] (see Section 3.1 of the RBDS Standard)

= version code = 1 bit (see Section 3.1 of the RBDS Standard)

TP = Traffic Program Identification code = 1 bit (see Section 3.2.1.3 of the RBDS Standard)

PTY = Program Type code = 5 bits PT[4:0] (see Section 3.2.1.2 and annex F of the RBDS Standard)

< t

: Block 1 of any particular group is transmitted first and block 4 last

Although the common data format is complex across 32 different group types, it can be defined at a high level as

follows:

Block 1:

Block 1 of every RDS group contains the 16 bit PI (pronounced "pie") code, or Program Identification

code.

For Europe, the PI code contains information related to the country of the broadcasting station,

coverage area and program reference. In all cases the PI code for identical programs on different

stations will be identical. This information, along with the optional alternate frequency list broadcast in

group 0A, can be used for automatically switching between frequencies.

For North America, the PI code is calculated from the station call letters, with five exceptions. Refer to

[1] for more information. The exceptions include modifications to the calculated PI code in some cases

for RDS/RBDS compatibility, a lookup table rather than calculation for stations with only three call

letters, and a lookup table for regionally or nationally linked radio stations with different call letters.

Alternate frequency switching is allowed for regionally or nationally linked radio stations when an

alternate frequency list is broadcast in group 0A.

Determining the country of origin of the broadcast is possible if the Extended Country Code (ECC) is

broadcast in group 1A and a look-up table is included at the presentation level. With this information it

is possible to properly configure the tuner for FM band edges, tuning steps, de-emphasis, Program

Type Code (PTY) definitions and other country-specific settings.

Block 2:

Block 2 contains the RDS Group Type code, Version Code, Traffic Program Code (TP), Program Type

Code (PTY), and five (5) unassigned message bits shown to the right of the PTY code in Figure 3.

Group Type Code - The group type code contains four bits and indicates what RDS Group the data

blocks represent. As mentioned previously, there are 32 possible group types ranging from basic

tuning information or emergency warnings, to "Open Data Applications." The RDS Groups are

Rev. 0.2

AN243

AN243概述

文档预览

推荐资源