Abstract:
A digital broadcast receiver has a first module that uses a conditional access card to receive a digital broadcast signal protected by scrambling, and a second module that receives a digital broadcast signal not protected by scrambling. Each module decodes its own received signal, and the second module selects and outputs one of the decoded signals. Each module includes its own controller. The controller in the first module executes application programs downloaded with the scrambled digital broadcast signal. The controller in the second module executes embedded application programs. Software troubleshooting is simplified because the two types of application programs run on separate controllers, and power consumption can be reduced by switching off the power of the first module when the conditional access card is not inserted.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a digital broadcast receiver, more specifically to a digital broadcast receiver conforming to the OpenCable standard. 
         [0003]    2. Description of the Related Art 
         [0004]    In recent years, many countries have begun to migrate from analog broadcasting to digital terrestrial broadcasting. Digitization of cable broadcasting is also proceeding, and an OpenCable broadcasting specification has been introduced in the U.S.A. and Korea. The OpenCable receiver specification is described in OpenCable Host Device 2.1 Core Functional Requirements OC-SP-HOST2.1-CFR-109-090904. 
         [0005]    The OpenCable specification describes a conditional access card, referred to as a CableCARD, a trademark, for decrypting conditional access encryption and transferring out-of-band (OOB) signals. An exemplary OpenCable receiver using a CableCARD has been disclosed in Japanese Patent Application Publication No. 2008-510352 (WO2006/016760). 
         [0006]    In a conventional digital broadcasting receiver, the application programs, such as user interfaces and tuning programs, are all embedded, whereas an OpenCable receiver (“OpenCable” is a trademark) includes embedded OpenCable Applications Platform (OCAP) middleware for executing application programs downloaded from broadcasting stations (cable TV stations). These application programs are used only for receiving cable broadcasts, so conventional embedded programs must be used to control the receiving of terrestrial broadcast signals, digital versatile disc (DVD) signals, and other external signals. 
         [0007]    The OpenCable specification does not specify how the downloaded application programs are to coexist with the embedded application programs. Japanese Patent Application Publication No. 2008-310553 describes a method in which both types of application programs reside on a single controller and one type of program or the other is selected according to the controller&#39;s start-up mode. 
         [0008]    An OpenCable digital broadcast receiver must include not only an interface for the cable card, but also an out-of-band signal transmitting-receiving circuit and a cable modem conforming to the Data Over Cable Service Interface Specification (DOCSIS), but all this circuitry takes up space and consumes power. Another problem is that if the downloaded application programs and embedded application programs share the same tuner and other hardware resources, the software becomes complex, and if both types of applications operate on the same control device, then when problems occur, troubleshooting takes extra time. 
       SUMMARY OF THE INVENTION 
       [0009]    One object of the invention is to provide a digital broadcast receiver with a simple system configuration. 
         [0010]    Another object of the present invention is to provide a digital broadcast receiver with reduced power consumption. 
         [0011]    Still another object is to provide a more convenient digital broadcast receiver. 
         [0012]    A digital broadcast receiver according to the invention has a first module and a second module. 
         [0013]    The first module includes a first receiver for receiving a digital broadcast signal protected by conditional access, such as a cable broadcast signal. The first module also includes a first interface for connection with a conditional access card operable to decrypt the digital broadcast signal protected by conditional access, a first decoder for decoding the signal decrypted by the conditional access card, an output unit for encrypting an output of the first decoder to generate an encrypted output signal, and a first controller for controlling the above components, downloading an application program received together with the digital broadcast signal, and executing the application program. 
         [0014]    The second module includes an input unit for receiving and decrypting the encrypted output signal to generate a first output signal, a second receiver for receiving a digital broadcast signal not protected by conditional access, a second decoder for decoding this digital broadcast signal to generate a second output signal, a display processor for selecting, processing, and outputting the first or second output signal as selected by the user, and a second controller for controlling the input unit, second receiver, second decoder, and display processor. 
         [0015]    The second controller may also execute application programs, but these are embedded application programs. 
         [0016]    The first module may include a power source that is switched off by the second controller when the conditional access card is not inserted. 
         [0017]    The second controller may prevent the display processor from selecting the signal received from the first module when the conditional access card is not inserted. 
         [0018]    When the conditional access card is not inserted, the second module may receive a cable broadcast signal and the second controller may construct a map in a memory indicating cable broadcast channels not protected by conditional access. 
         [0019]    The second controller preferably controls all power-on/off switching and audio volume adjustment operations, controls channel selection and tuning operations by the second receiver, and processes the relevant commands input by the user. When the conditional access card is inserted and the display processor selects the first output signal, the first controller preferably controls channel selection and tuning operations by the first receiver, and processes the relevant commands input by the user. 
         [0020]    The first module may also include an on-screen display processor. If the first receiver receives high-priority emergency warning information, the on-screen display processor overlays the warning information on the output of the first decoder and the first controller instructs the second controller to have the display processor select the signal received by the input unit. If the first receiver receives low-priority emergency warning information, the first controller sends the emergency warning information to the second controller through a communication link and the second controller processes the emergency warning information. 
         [0021]    The digital broadcast receiver has a simple modular structure that facilitates efficient manufacturing. 
         [0022]    Power consumption can be reduced by switching the power of the first module off when the conditional access card is not inserted. 
         [0023]    The digital broadcast receiver is convenient because downloaded application programs operate on one controller and embedded application programs operate on another controller, so that when software problems occur, troubleshooting is simplified. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    In the attached drawings: 
           [0025]      FIG. 1  is a block diagram illustrating a digital broadcast receiver in a first embodiment of the invention; 
           [0026]      FIG. 2  is a block diagram illustrating a portion of the digital broadcast receiver in a second embodiment of the invention; 
           [0027]      FIG. 3  is a block diagram illustrating a portion of the digital broadcast receiver in a third embodiment of the invention; 
           [0028]      FIG. 4  is a block diagram illustrating a portion of the digital broadcast receiver in a fourth embodiment of the invention; and 
           [0029]      FIG. 5  is a block diagram illustrating a portion of the digital broadcast receiver in a fifth embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    Embodiments of the invention will now be described with reference to the attached drawings, in which like elements are indicated by like reference characters. 
       First Embodiment 
       [0031]    Referring to  FIG. 1 , the digital broadcast receiver in the first embodiment has a basic module  100  for receiving digital terrestrial broadcasts and the like, and an auxiliary module  200  for receiving cable broadcasts. The basic module  100  includes a pair of input terminals  101 ,  102 , a tuner  103 , an Advanced Television Standards Committee/quadrature amplitude modulation (ATSC/QAM) demodulator  104 , a decoder  105 , a display processor  106 , a host central processor (CPU)  108 , a high-definition multimedia interface (HDMI) receiver  109 , an interface  110 , and a command receiver  112 . 
         [0032]    The command receiver  112  receives signals from a command input unit  113  such as, for example, a keyboard or a remote control. The user uses the command input unit  113  to enter operating commands, which the command receiver  112  sends to the host CPU  108 . 
         [0033]    The auxiliary module  200  includes an input-output terminal  210 , a switch  211 , a diplexer  212 , tuners  213 ,  215 ,  218 , a QAM demodulator  214 , a quadrature phase shift keying (QPSK) demodulator  216 , a QPSK modulator  217 , a QAM demodulator  219 , a DOCSIS processor  220 , a QAM modulator  221 , a decoder  223 , a host CPU  224 , a power source  225 , an HDMI transmitter  226 , and a CableCARD interface  227 . 
         [0034]    A CableCARD  222  is detachably inserted into the auxiliary module  200  as a conditional access card. When inserted into the auxiliary module  200 , the CableCARD  222  is connected to QAM demodulator  214 , QPSK demodulator  216 , QPSK modulator  217 , decoder  223 , and host CPU  224  through the CableCARD interface  227 . 
         [0035]    The basic module  100  is integrally mounted in the digital broadcast receiver. The auxiliary module  200  is detachably mounted in the digital broadcast receiver. When mounted in the digital broadcast receiver, the auxiliary module  200  is electrically connected to the basic module  100  through the interface  110  as shown in  FIG. 1 , but this connection is detachable. 
         [0036]    Signals pass in both directions through the input-output terminal  210  of the auxiliary module  200 . The diplexer  212  separates the incoming signals from the outgoing signals. The incoming signals are received cable broadcast signals, including audio and video signals that the diplexer  212  passes to tuner  213 , GOB signals that the diplexer  212  passes to tuner  215 , and DOCSIS signals that the diplexer  212  passes to tuner  218 . 
         [0037]    Tuner  213  tunes to a video signal channel. QAM demodulator  214  demodulates the tuned video channel signal to a bitstream and passes the bitstream to the CableCARD  222 . This bitstream has been encrypted (scrambled) for conditional access. The CableCARD  222  decrypts (descrambles) the bitstream. 
         [0038]    The CableCARD  222  passes the descrambled bitstream, which is still encrypted by the Data Encryption Standard (DES) algorithm, to decoder  223 . Decoder  223  decrypts the DES encryption and decodes the decrypted bitstream to reproduce the baseband video signal. 
         [0039]    An audio signal is similarly reproduced, but for simplicity, only the reproduction of a video signal will be described below. 
         [0040]    Tuner  215  is tuned to receive an GOB signal. QPSK demodulator  216  demodulates the GOB signal into a datastream and passes the datastream to the CableCARD  222 . From the GOB signal, the CableCARD  222  obtains a decryption signal (key) for decrypting the conditional access decryption, or information describing currently broadcast programs. GOB signal content is specified by a Society of Cable Telecommunications Engineers standard (SCTE  55 ). The CableCARD  222  communicates with host CPU  224  through the CableCARD interface  227 . 
         [0041]    Through the CableCARD interface  227 , signals pass from QAM demodulator  214  and QPSK demodulator  216  to the CableCARD  222  and from the CableCARD  222  to the QPSK modulator  217  and decoder  223 . 
         [0042]    When the digital broadcast receiver sends a datastream to the broadcast station, such as a datastream requesting video-on-demand or a unique device identifier for releasing the conditional access encryption, the CableCARD interface  227  passes the datastream to the diplexer  212  through QPSK modulator  217  and the switch  211 . The diplexer  212  restricts this outgoing signal to a specified frequency band, differing from the frequency bands of the incoming signals, so that the incoming and outgoing signals do not interfere with each other. 
         [0043]    Tuner  218  is tuned to receive a DOCSIS signal. QAM demodulator  219  demodulates the DOCSIS signal to a datastream, and the DOCSIS processor  220  decodes the datastream. The OpenCable specification specifies that GOB signals are transmitted by the DOCSIS system using the DOCSIS Set-Top Gateway (DSG) system. Because a broadcast station may choose either the GOB system or the DOCSIS system, although the digital broadcast receiver includes both GOB and DOCSIS signal circuits, only one of these two signal circuits is actually used. 
         [0044]    When the digital broadcast receiver sends DOCSIS signals to the broadcast station, the DOCSIS signals are modulated by the QAM modulator  221  and pass through the switch  211  to the diplexer  212 . 
         [0045]    Host CPU  224  communicates with the CableCARD  222  through the CableCARD interface  227 , determines from the signal received from the CableCARD  222  whether the GOB system or the DOCSIS system is used by the cable system in which the digital broadcast receiver is installed, selects the GOB signal circuit or the DOCSIS signal circuit, and controls the switch  211  accordingly. When the GOB signal circuit is used, GOB signals are passed from the QPSK modulator  217  to the diplexer  212 ; when the DOCSIS signal circuit is used, DOCSIS signals are passed from the QAM modulator  221  to the diplexer  212 . 
         [0046]    Host CPU  224  controls the circuits in the auxiliary module  200 , including the tuners  213 ,  215 ,  218 , demodulators  214 ,  216 ,  219 , modulators  217 ,  221 , DOCSIS processor  220 , decoder  223 , HDMI transmitter  226 , and CableCARD interface  227 , and controls the CableCARD  222 . Host CPU  224  includes embedded OCAP middleware and uses a boot memory and working memory (not shown) to operate autonomously. Host CPU  224  also receives application programs sent as part of the datastreams described above, and executes the application programs on the OCAP middleware to implement different services such as Electronic Program Guide (EPG) and video-on-demand services. Accordingly, host CPU  224  may obtain viewing and listening application programs transmitted by a broadcasting station by downloading them via the broadcast signal. 
         [0047]    The power source  225  in the auxiliary module  200  supplies power to host CPU  224  and the circuits it controls in the auxiliary module  200 . This power source  225  is turned on and off independently of the operation of the power source (not shown) for the basic module  100  and the other parts of the digital broadcast receiver. 
         [0048]    Input terminal  101  in the basic module  100  normally receives terrestrial broadcast signals, but may be connected to receive cable broadcast signals as well. The basic module  100  can process cable broadcast signals successfully if they are not protected by conditional access. Tuner  103  is tuned to a desired video signal channel. The ATSC/QAM demodulator  104  demodulates the tuned video channel signal to a bitstream. Decoder  105  decodes the demodulated bitstream. 
         [0049]    Input terminal  102  receives baseband video signals other than broadcast signals, such as video signals reproduced from a DVD. Signals input from input terminal  102  or output from the decoder  105  enter the display processor  106 . 
         [0050]    Host CPU  108  controls the circuits in the basic module  100 , and uses a boot memory and working memory (not shown) to operate autonomously by executing predetermined embedded programs. 
         [0051]    Tuner  103  and the ATSC/QAM demodulator  104  constitute the receiver of the basic module  100 ; tuners  213 ,  215 ,  218  and demodulators  214 ,  216 ,  219  constitute the receiver of the auxiliary module  200 . 
         [0052]    Signals output from the decoder  223  in the auxiliary module  200  pass to the display processor  106  through the interface  110  in the basic module  100 . Under control of host CPU  108 , the display processor  106  selects the signal received from the auxiliary module  200  (the first output signal), the signal received from decoder  105  (the second output signal), or the signal received from input terminal  102 , performs different adjustments, produces a final output signal, and sends the final output signal to a display unit  115  through an output terminal  107 . Host CPU  108  controls the selection made by the display processor  106  according to commands entered by the user using the command input unit  113 . 
         [0053]    Signals that pass from decoder  223  to the display processor  106  are encrypted for content protection, using an interface such as the High-Definition Multimedia Interface (HDMI). The HDMI transmitter  226  therefore converts the format of the video data received from decoder  223  to the HDMI format, a process that includes encryption of the video data, and sends the converted video data to the HDMI receiver  109  through the interface  110  in the basic module  100  as an encrypted output signal. The HDMI receiver  109  decrypt the encrypted output signal and restores the received HDMI video data to the original format. The HDMI transmitter  226  accordingly operates as an output unit that sends signals from the auxiliary module  200  to the basic module  100 , and the HDMI receiver  109  in the basic module  100  operates as an input unit that receives signals from the auxiliary module  200 . 
         [0054]    To enable the two modules  100 ,  200  to cooperate, host CPU  108  communicates with host CPU  224  through a communication link  235  such as, for example, a Universal Asynchronous Receiver Transmitter (UART) link. 
         [0055]    The auxiliary module  200  operates only when the CableCARD  222  is inserted. More specifically, when the CableCARD  222  is not inserted, the digital broadcast receiver is permitted to process only signals not protected by conditional access, and cannot use OOB signals. Only the basic module  100  can then operate. Accordingly, even if the digital broadcast receiver includes the OCAP auxiliary module  200 , by not inserting the CableCARD  222  the user can choose not to use the cable broadcast receiving function temporarily, or semi-permanently. 
         [0056]    The CableCARD interface  227  for the CableCARD  222  conforms to the Personal Computer Card (PC Card) standard, and has a pair of card detection pins  229  at each end (only one pair is shown in  FIG. 1 ). The card detection pins  229  are pulled up to the power supply potential of the basic module  100  when the CableCARD  222  is not inserted, and fall to the ground potential when the CableCARD  222  is inserted. Host CPU  108  in the basic module  100  determines whether the CableCARD  222  is inserted by receiving a detection signal obtained from the detection pins  229 . When the CableCARD  222  is not inserted into the auxiliary module  200  and the card detection pins  229  are at the power supply potential, host CPU  108  halts the operation of the auxiliary module  200  by turning off its power source  225 . 
         [0057]    When the power source  225  is turned off, if the CableCARD  222  is inserted, host CPU  108  detects that the CableCARD  222  is inserted because the card detection pins  229  fall to the ground potential, turns on the power source  225 , starts up the auxiliary module  200 , communicates with host CPU  224  through the communication link  235 , notifies host CPU  224  of the insertion of the CableCARD  222 , and allows host CPU  224  to activate the CableCARD  222 . 
         [0058]    As described above, when the CableCARD  222  is not inserted, host CPU  108  avoids unnecessary power consumption by preventing the power source  225  from supplying power to the auxiliary module  200 . In addition, since host CPU  224  executes downloaded application programs and host CPU  108  executes embedded application programs, when software problems occur, troubleshooting is simplified. Moreover, the detachable mounting of the auxiliary module  200  in the digital broadcast receiver facilitates selective manufacturing of a basic digital broadcast receiver including only the basic module  100  and a multifunctional digital receiver including both the basic module  100  and the auxiliary module  200 . 
       Second Embodiment 
       [0059]    The digital broadcast receiver in the second embodiment has a generally identical configuration as the digital broadcast receiver in the first embodiment.  FIG. 2  shows the display processor  106 , host CPU  108 , HDMI receiver  109 , interface  110 , and command receiver  112  in the basic module  100 , the command input unit  113  and display unit  115 , and the decoder  223 , host CPU  224 , power source  225 , HDMI transmitter  226 , and communication link  235  in the auxiliary module  200 . The digital broadcast receiver in the second embodiment also has input terminals  101 , and  102 , tuners  103 ,  213 ,  215 ,  218 , demodulators  104 ,  214 ,  216 , and  219 , decoder  106 , input-output terminal  210 , diplexer  212 , modulators  217 , and  221 , DOCSIS processor  220 , CableCARD interface  227 , for connection with CableCARD  222 , and card detection pins  229 , which are shown in  FIG. 1 , but they are omitted from  FIG. 2 . 
         [0060]    The second embodiment operates in substantially the same way as the first embodiment, but with the following difference. 
         [0061]    As in the first embodiment, host CPU  108  receives a detection signal obtained from the card detection pins  229  and determines whether the CableCARD  222  is inserted. 
         [0062]    When host CPU  108  determines that the CableCARD  222  is not inserted, since the auxiliary module  200  does not necessarily have to operate, host CPU  108  may turn off its power source  225  as in the first embodiment, or switch the auxiliary module  200  into a standby state. In this state, no signal is output from decoder  223 . If the display processor  106  selects input from the auxiliary module  200  in this state and sends the selected but nonexistent signal to the display unit  115 , the user may mistake the resulting blank display for a device failure. Host CPU  108  therefore allows the display processor  106  to select only the signals received from input terminal  102  and decoder  105  and prevents the display processor  106  from selecting the signal received from decoder  223 . That is, host CPU  108  allows the display processor  106  to select only signals with significant display data, prevents the display of nonexistent signals, and thereby avoids confusing the user. 
       Third Embodiment 
       [0063]    The digital broadcast receiver in the third embodiment has a generally identical configuration as the digital broadcast receiver in the first embodiment, but differs from the digital broadcast receiver in the first embodiment by adding a memory  120  for storing a channel map, and by operations described below.  FIG. 3  shows the display processor  106 , host CPU  108 , HDMI receiver  109 , interface  110 , command receiver  112 , and memory  120  in the basic module  100 , the command input unit  113  and display unit  115 , and the decoder  223 , host CPU  224 , power source  225 , HDMI transmitter  226 , and communication link  235  in the auxiliary module  200 . The digital broadcast receiver in the third embodiment also has input terminals  101 , and  102 , tuners  103 ,  213 ,  215 ,  218 , demodulators  104 ,  214 ,  216 , and  219 , decoder  106 , input-output terminal  210 , diplexer  212 , modulators  217 , and  221 , DOCSIS processor  220 , CableCARD interface  227 , for connection with CableCARD  222 , and card detection pins  229 , which are shown in  FIG. 1 , but they are omitted from  FIG. 3 . 
         [0064]    The difference between the first and third embodiments is that a channel map is created in the memory  120 . 
         [0065]    As in the first and second embodiments, host CPU  108  receives a detection signal obtained from the card detection pins  229  and determines whether the CableCARD  222  is inserted. 
         [0066]    When host CPU  108  determines that the CableCARD  222  is not inserted, since the auxiliary module  200  does not necessarily have to operate, host CPU  108  may switch the auxiliary module  200  into a standby state or turn off its power source  225 . In this state it is still possible to receive cable broadcast signals if they are not protected by conditional access. More specifically, the receiver section  103 ,  104  of the basic module  100  can receive these cable broadcast signals under control of host CPU  108 , and the basic module  100  processes the received cable broadcast signals. To facilitate this process, host CPU  108  generates a channel map by storing information identifying receivable signal channels in the memory  120  in the basic module  100 . The channel map is then used in subsequent channel tuning. 
         [0067]    When host CPU  108  determines that the CableCARD  222  is not inserted, if the user enters a channel scanning command as part of an initial setting process, host CPU  108  uses the basic module  100  to scan all cable broadcast channels. On detecting a channel with a signal not protected by conditional access, host CPU  108  stores the relevant channel information in the memory  120 . If the user later enters a tuning command such as a channel up or down command by using the command input unit  113  and command receiver  112 , host CPU  108  reads the channel information stored in the memory  120  and tunes to an unprotected video signal channel. 
         [0068]    In the third embodiment, even a user who does not have a CableCARD  222  can continue to view and listen to cable broadcasts not protected by conditional access. 
       Fourth Embodiment 
       [0069]    The digital broadcast receiver in the fourth embodiment has a generally identical configuration as the digital broadcast receiver in the first embodiment, but is provided with an additional communication link  236 , and operations differ as described below.  FIG. 4  shows the display processor  106 , HDMI receiver  109 , interface  110 , command receiver  112 , and host CPU  108  in the basic module  100 , the command input unit  113  and display unit  115 , and the decoder  223 , host CPU  224 , power source  225 , HDMI transmitter  226 , and communication link  235  in the auxiliary module  200 . The digital broadcast receiver in the fourth embodiment also has input terminals  101 , and  102 , tuners  103 ,  213 ,  215 ,  218 , demodulators  104 ,  214 ,  216 , and  219 , decoder  106 , input-output terminal  210 , diplexer  212 , modulators  217 , and  221 , DOCSIS processor  220 , CableCARD interface  227 , for connection with CableCARD  222 , and card detection pins  229 , which are shown in  FIG. 1 , but they are omitted from  FIG. 4 . 
         [0070]    The fourth embodiment operates in substantially the same way as the first embodiment, but with the following difference. 
         [0071]    In the fourth embodiment, the command receiver  112  passes commands received from the command input unit  113  directly to the host CPU  108  in the basic module  100  and, through the interface  110 , directly, i.e., without passing through the CPU  108 , to the host CPU  224  in the auxiliary module  200 . For this passage of the commands, the additional communication link  236  is used. The two host CPUs  108 ,  224  are also interconnected through the interface  110  and communication link  235 , however, and through this route, the two host CPUs  108 ,  224  exchange and share information indicating the signal selected by the user. 
         [0072]    As in the first to third embodiments, the host CPU  108  in the basic module  100  receives a detection signal obtained from the card detection pins  229  and determines whether the CableCARD  222  is inserted. 
         [0073]    When host CPU  108  determines that the CableCARD  222  is not inserted, host CPU  108  controls the selection made by the display processor  106  according to commands entered by the user using the command input unit  113  and command receiver  112 . The display processor  106  selects the signal received from input terminal  102  or the signal received from decoder  105 , and produces an output signal. In addition, host CPU  108  processes all power-on/off switching operations, channel selection operations such as channel up/down operations, and audio volume adjustment operations, including mute control, in the digital broadcast receiver. Host CPU  108  also processes all key operations, such as number key operations and up-down-right-left arrow key operations on menus, including broadcast program selection menus and menus for various other functions. 
         [0074]    Even when host CPU  108  detects that the CableCARD  222  is inserted, if a command entered by the user instructs host CPU  108  to have the display processor  106  select the signal received from input terminal  102  or decoder  105 , host CPU  108  processes all the operations noted above. 
         [0075]    When host CPU  108  detects that the CableCARD  222  is inserted and the user command has the display processor  106  select the signal received from decoder  223 , however, host CPU  224  executes a downloaded application program to process tuning operations such as, for example, channel up/down operations, and key operations such as, for example, the menu operations noted above. Host CPU  108  continues to process power-on/off switching operations and audio volume adjustment operations, including mute control. 
         [0076]    In short, host CPU  108  always knows whether the CableCARD  222  is inserted or not and which input the user has selected, and this information determines its processing duties. Host CPU  224  learns whether the CableCARD  222  is inserted or not and which input the user has selected by communicating with host CPU  108  through the interface  110  and communication link  235 , and performs the processing that is not performed by host CPU  108 . 
         [0077]    This arrangement enables host CPU  108  to maintain consistent power control and audio volume control, while at the same time enabling channel selection operations and menu operations to be processed by the appropriate host CPU: the host CPU  224  in the auxiliary module  200  when the CableCARD  222  is inserted and the user selects the signal from decoder  223  in the auxiliary module  200 ; the host CPU  108  in the basic module  100  in other cases. All commands and operations input by the user can therefore be appropriately executed. 
         [0078]    In a variation of the fourth embodiment, commands entered by the user via the command input unit  113  and command receiver  112  are sent only to host CPU  108  and are not sent directly to host CPU  224  as described above. Host CPU  108  receives the commands and then sends them through the interface  110  and communication link  235  to host CPU  224 , adding information indicating whether the CableCARD  222  is inserted and which input the user has selected. 
       Fifth Embodiment 
       [0079]    The digital broadcast receiver in the fifth embodiment has a generally identical configuration as the digital broadcast receiver in the first embodiment, but differs from the digital broadcast receiver in the first embodiment by including an additional on-screen display (OSD) processor, and by operations described below.  FIG. 5  shows the display processor  106 , HDMI receiver  109 , interface  110 , command receiver  112 , and host CPU  108  in the basic module  100 , the command input unit  113  and display unit  115 , and the decoder  223 , host CPU  224 , power source  225 , HDMI transmitter  226 , communication link  235 , and OSD processor  241  in the auxiliary module  200 . The digital broadcast receiver in the fifth embodiment also has input terminals  101 , and  102 , tuners  103 ,  213 ,  215 ,  218 , demodulators  104 ,  214 ,  216 , and  219 , decoder  106 , input-output terminal  210 , diplexer  212 , modulators  217 , and  221 , DOCSIS processor  220 , CableCARD interface  227 , for connection with CableCARD  222 , and card detection pins  229 , which are shown in  FIG. 1 , but they are omitted from  FIG. 5 . 
         [0080]    The fifth embodiment operates in substantially the same way as the first embodiment, but with the following difference. In the fifth embodiment, the OSD processor  241  performs processing for displaying characters indicating emergency warning information overlaid on video data. The display processor  106  can also perform similar overlay display processing. 
         [0081]    As in the first to fourth embodiments, the host CPU  108  in the basic module  100  receives a detection signal obtained from the card detection pins  229  and determines whether the CableCARD  222  is inserted. 
         [0082]    When the CableCARD  222  is inserted and the auxiliary module  200  operates, the auxiliary module  200  may receive emergency warning information. Emergency warning information display may be mandated by the government, as in the United States, for example, where the emergency warning information is referred to as an Emergency Alert System (EAS) message. 
         [0083]    When the display processor  106  is using the signal received from the auxiliary module  200  to produce an output signal, if the auxiliary module  200  receives emergency warning information and host CPU  224  detects that an EAS message is received, the auxiliary module  200  receives and processes the EAS signal. Depending on the content of the EAS message, the OSD processor  241  may overlay characters indicating the message on the video data, or tune in a specified broadcast channel that broadcasts the EAS message and relevant detailed information. 
         [0084]    When the display processor  106  is using the signal received from input terminal  102  or decoder  105  to produce the final output signal, if the auxiliary module  200  receives emergency warning information and host CPU  224  detects that an EAS message is received, the auxiliary module  200  receives and processes the EAS signal. Host CPU  224  determines the priority of the EAS message packet. If the priority exceeds a predetermined value, for example, ‘eleven’, the auxiliary module  200  and the OSD processor  241  perform all the operations noted above, and host CPU  224  sends a request for forced signal switching to host CPU  108  through the communication link  235 . On receiving the request, host CPU  108  controls the display processor  106  so as to pass the broadcast channel signal with the EAS message and relevant detailed information received from the auxiliary module  200  to output terminal  107 . 
         [0085]    If host CPU  224  determines that the priority of the message packet is lower than the predetermined value of, for example, ‘eleven’, the OSD processor  241  does not display the message but sends the message packet to host CPU  108  through the communication link  235 . Host CPU  108  restores the received message to its original format, thereby recovering the message before conversion. The display processor  106  displays the message overlaid on the video data currently being viewed. 
         [0086]    As described above, in the fifth embodiment, when the auxiliary module  200  receives an EAS message, it may be processed by either host CPU  224  or host CPU  108 , depending on the priority of the EAS message. Regardless of which input signal the user has selected and which video data are being displayed, when an EAS message is received, host CPU  224  or host CPU  108  can display the EAS message as appropriate for its priority. 
         [0087]    When the CableCARD  222  is not inserted, if the basic module  100  receives emergency warning information and host CPU  108  detects that an EAS message is received, host CPU  108  determines the priority of the EAS message packet. Depending on the priority, the display processor  106  may overlay characters indicating the message on the video data, or tune in a specified broadcast channel that broadcasts the EAS message and relevant detailed information. 
         [0088]    The first to fifth embodiments can be combined. For example, the first embodiment, which turns off the power source  225  in the auxiliary module  200  when the CableCARD  222  is not inserted, can be combined with the digital broadcast receivers in the second to fourth embodiments. Accordingly, the power source  225  is shown in the auxiliary module  200  in  FIGS. 2 to 5  as well as in  FIG. 1 . In the second to fifth embodiments, however, the auxiliary module  200  does not necessarily have to include a power source  225 ; the power source (not shown) in the basic module  100  may supply power to the circuits in the auxiliary module  200 . 
         [0089]    The second embodiment, in which the display processor  106  in the basic module  100  cannot select the signal output from the auxiliary module  200  when the CableCARD  222  is not inserted, may be combined with the digital broadcast receivers in the first, third, fourth, and fifth embodiments. 
         [0090]    The third embodiment, in which the basic module  100  receives cable broadcast signals not protected by conditional access and creates a channel map thereof, may be similarly combined with the digital broadcast receivers in the first, second, fourth, and fifth embodiments. 
         [0091]    The fourth embodiment, in which the command receiver  112  passes commands directly to the host CPU  224  in the auxiliary module  200  and operations are processed by either host CPU  108  or host CPU  224 , as appropriate, may be combined with the digital broadcast receivers in the first, second, third, and fifth embodiments. 
         [0092]    The emergency warning information processing described in the fifth embodiment may be added to the digital broadcast receivers in the first to fourth embodiments. 
         [0093]    Those skilled in the art will recognize that further variations are possible within the scope of the invention, which is defined in the appended claims.