Subscriber terminal with plug in expansion card

What is claimed is:

1. A subscriber terminal for a subscription television system, comprising;

control processor means operative for executing a control program for controlling the features of the subscriber terminal;

memory means for storing data and at least a portion of said control program for said control processor means;

a memory bus including data, address, and control lines for coupling said control processor means to said memory means; and

expansion means coupled to said memory bus for coupling to an optional second memory means for storing other portions of said control program when said optional second memory means is present.

2. A subscriber terminal as set forth in claim 1 further comprising:

authorization circuitry for permitting access to restricted channels of the subscription television system;

secure processor means for controlling said authorization circuitry; and

a secure processor bus for coupling said secure processor means to said expansion means,

whereby said expansion means further provides renewed or additional security for the subscriber terminal.

3. A subscriber terminal as set forth in claim 2 wherein:

said secure processor bus is coupled to said expansion means, and

wherein said expansion means is coupled to an optional second secure processor means for providing renewed or additional security for the subscriber terminal.

4. A subscriber terminal as set forth in claim 1 wherein said expansion means comprises:

a printed circuit board connector adapted to receive a plug-in printed circuit board module.

5. A subscriber terminal as set forth in claim 1 which further includes: a printed circuit board (PCB) module coupled to said expansion means.

6. A subscriber terminal as set forth in claim 5 wherein:

said PCB module includes said optional second memory means coupled to said memory bus.

7. A subscriber terminal as set forth in claim 2 which further includes: a printed circuit board (PCB) module coupled to said expansion means.

8. A subscriber terminal as set forth in claim 7 wherein:

said PCB module includes a second secure processor coupled to said secure processor bus.

9. A subscription terminal as set forth in claim 8 wherein:

said PCB module includes additional memory coupled to said memory bus.

10. A subscriber terminal as set forth in claim 1, wherein said expansion means comprises:

an expansion slot provided in said subscriber terminal for receiving a printed circuit board.

11. A subscriber terminal as set forth in claim 10, wherein said optional second memory means comprises memory circuitry mounted to said printed circuit board.

12. A subscriber terminal as set forth in claim 10, further comprising means for detecting when said optional second memory means is present in said expansion slot, and

wherein said control processor means is operative to begin executing said control program from said memory means or from said optional second memory means in response to detection that said optional second memory means is present.

13. A subscriber terminal as set forth in claim 3 wherein said optional second secure processor means comprises a secure microprocessor mounted to a printed circuit board, and wherein said expansion means comprises an expansion slot provided in said subscriber terminal for receiving said printed circuit board.

14. A method of operating a subscriber terminal for a subscription television system, said subscriber terminal including:

a control processor for controlling the features of the subscriber terminal;

an internal memory for storing data and instructions for the control microprocessor;

a memory bus including data, address, and control lines for coupling the control processor to the internal memory;

authorization circuitry for permitting access to restricted channels of the subscription television system;

a secure processor for controlling the authorization circuitry; and

a secure processor bus for coupling the secure processor to the authorization circuitry,

the method comprising the steps of:

providing an expansion slot in the subscriber terminal for coupling to the internal memory and allowing expansion of the internal memory, and for coupling to the secure processor bus;

providing a logic signal indicative of the presence of an expansion card in the expansion slot;

in the control microprocessor, testing the logic signal to determine the presence of the expansion card in the expansion slot; and

in response to a determination that the expansion card is present in the expansion slot, setting system parameters of the subscriber terminal to allow communication with and control of circuitry on the expansion card.

15. The method of claim 14, further comprising the step:

in response to a determination that the expansion card is not present in the expansion slot, setting system parameters of the subscriber terminal to internal values so that the control microprocessor begins executing program code stored in the internal memory.

16. The method of claim 14, wherein the expansion card includes an external memory, and further comprising the step:

in response to a determination that the expansion card is present in the expansion slot, setting system parameters of the subscriber terminal to external values so that the control microprocessor begins executing program code stored in the external memory.

17. In a subscription television system providing a plurality of restricted and unrestricted channels in which signals are transmitted to subscriber terminals from a head end, a subscriber terminal comprising:

a control microprocessor for controlling the operation of the subscriber terminal;

an internal memory for storing data and instructions for said control microprocessor, said internal memory coupled to said control microprocessor; and

an expansion means for receiving an optional expansion circuit module;

said control microprocessor operative for:

receiving a download program code parameters transaction from the head end of said subscription television system, said download program code parameters transaction including a destination for new program code for the subscriber terminal;

detecting the presence of said optional expansion circuit module;

receiving a download program code transaction from the head end of said subscription system, said download program code transaction containing new program code for the subscriber terminal;

in response to detection of said optional external circuit module, downloading said new program code from said download program code transaction into said optional expansion circuit module.

18. The subscriber terminal of claim 17, wherein said control microprocessor detects the presence of said optional expansion circuit module by testing the state of a logic signal associated with said optional expansion circuit module.

19. The subscriber terminal of claim 17, wherein said optional expansion circuit module contains external memory, and wherein said new program code is loaded into said external memory.

20. The subscriber terminal of claim 19, wherein said control microprocessor is operative for:

in response to detection that said optional expansion circuit module is not present, setting system parameters of the subscriber terminal to internal values so that said control microprocessor begins executing program code stored in said internal memory.

21. The subscriber terminal of claim 19, wherein said control microprocessor is operative for:

in response to detection that said optional expansion circuit module is present, setting system parameters of the subscriber terminal to external values so that said control microprocessor begins executing program code stored in said external memory.

22. The subscriber terminal of claim 17, wherein said new program code is for said control microprocessor.

23. The subscriber terminal of claim 17, further comprising:

a secure microprocessor;

an internal memory associated with said secure microprocessor for storing authorization and control data for restricted channels;

said secure microprocessor operative for:

receiving a download program code parameters transaction from the head end of the subscription television system, said download program code parameters transaction containing authorization and control data for restricted channels, and

enabling said subscriber terminal to receive a restricted channel in accordance with said authorization and control data.

24. The subscriber terminal of claim 23, wherein said secure microprocessor is internal to the subscriber terminal.

25. The subscriber terminal of claim 23, wherein said secure microprocessor is located in said optional expansion circuit module.

26. In a subscription television system providing a plurality of restricted and unrestricted channels in which signals are transmitted to subscriber terminals from a head end, each of the subscriber terminals including a control microprocessor for controlling the operation of the subscriber terminal and an internal memory coupled to the control microprocessor for storing data and instructions for the control microprocessor, a method of operating a subscriber terminal, comprising the steps of:

providing an expansion means in the subscriber terminal for receiving an optional expansion circuit module;

receiving a download program code parameters transaction from the head end of said subscription system, the download program code parameters transaction including a destination for new program code for the subscriber terminal;

detecting the presence of the optional expansion circuit module;

receiving a download program code transaction from the head end of the subscription television system, the download program code transaction containing new program code for the subscriber terminal; and

in response to detection of the presence of the optional expansion circuit module, downloading the new program code from the download program code transaction into the optional expansion circuit module.

27. The method of claim 26, wherein the control microprocessor detects the presence of the optional expansion circuit module by testing the state of a logic signal associated with the optional expansion circuit module.

28. The method of claim 26, wherein the optional expansion circuit module contains external memory, and further comprising the step of loading the new program code into the external memory.

29. The method of claim 28, further comprising the step of:

in response to detection that the optional expansion circuit module is not present, setting system parameters of the subscriber terminal to internal values so that the control microprocessor begins executing program code stored in the internal memory.

30. The method of claim 28, further comprising the step of:

in response to detection that the optional expansion circuit module is present, setting system parameters of the subscriber terminal values so that the control microprocessor begins executing program code stored in the external memory.

31. The method of claim 26, wherein the new program code is for the control microprocessor.

32. The method of claim 26, further comprising the steps of:

providing a secure microprocessor associated with the subscriber terminal;

providing an internal memory associated with the secure microprocessor for storing authorization and control data for restricted channels;

receiving a download program code parameters transaction from the head end of the subscription television system, the download program code parameters transaction containing authorization and control data for restricted channels; and

with the secure microprocessor, enabling the subscriber terminal to receive at least one of the restricted channels in accordance with the authorization and control data.

33. The method of claim 32, wherein the secure microprocessor is internal to the subscriber terminal.

34. The method of claim 32, wherein the secure microprocessor is located in the optional expansion circuit module.

Description Submit all comments and votes

The invention pertains generally to subscriber terminals for subscription television systems and is more particularly directed to providing such terminals increased flexibility and additional features via expansion of their processing, memory or security features.

The subscriber terminal, more commonly known as a set top terminal, is an integral component of subscription television systems. These subscription television systems can be cable television (CATV) systems, SMATV systems, a multi-point, multidistribution subscription system (MMDS), or a direct-to-home (DTH) type of system. The terminals have conventionally provided the functions of tuning particular channels of the subscription system which are outside the subscriber's television receivers capability. Further, they provide conditional access to the particular subscription service through authorization codes and in many services provide tiering or authorization of particular channels of the service by descrambling.

More recently, the subscriber terminal has become user friendly by providing an interactive, on-screen display and other user functions that allow the subscriber to manipulate the cable service and his television receiver in additional manner. These features include such things as volume control, pay-per-view event confirmation, favorite channel listings, sleep timer features, parental control capability, messaging, program timers for recording VCR programs and other types of consumer friendly operational features.

In addition, some of the features found in newer television receivers can be provided for older receivers by the subscription terminal. For example, channel identifiers, mute and remote volume control can be accomplished by the subscriber terminal making the subscriber's television receiver appear to be a newer model with these capabilities.

An advantageous example of a subscriber terminal with these advanced consumer features is the 8600 Model series of subscriber terminals manufactured by Scientific-Atlanta, Inc. of Norcross, Ga.

The subscriber terminals generally operate under the control of a microprocessor which has a control program stored in a read only memory (ROM), or a non-volatile memory such as a EPROM. The subscriber terminal may also include other volatile memory such as DRAM to allow for the additional temporary storage of data and other information. The memory of whatever type is generally limited to the particular purposes and features that are originally designed for the subscriber terminal because of cost. Therefore, upgrades to the features of a subscriber terminal which require additional memory space usually demand replacement of at least the memory modules and/or the deletion of some of the presently installed features. If the control processor is not powerful enough to process the additional features, it must also be replaced with a consequent reprogramming of the central software.

Because of the wide dispersion and number of subscriber terminals in a subscription television system, several hundred thousand and usually one per household for a CATV system, the cost and difficulty of replacing such terminals on a system basis is prohibitive.

This prevents features which could be provided much sooner to subscribers to only be available over long phase in periods where one model is being taken out of service and another is being placed in service.

Further, it makes it difficult for a subscriber to obtain a full feature set of a subscriber terminal, even if he would pay for some features which are important to him. Additional features because of the extra hardware burden on each terminal must be justified on a system wide basis. If only a few subscribers will pay for an additional feature the cost system wide for the extra memory or processing power to provide the feature could outweigh any potential revenues from that feature.

What is needed is a way to individually and/or universally upgrade, add or change features without having to replace the entire subscriber terminal.

The difficulty of providing additional features for different consumers and upgrading has been addressed with varying degrees of success by some in the consumer industry. For example, many personal computer manufacturers provide a mother board which is attached to a bus connected to a number of expansion slots. Each expansion slot in this open architecture system can be used to configure a different system with the purchase of additional peripheral boards which plug into the slots.

An open architecture is somewhat incompatible with subscriber terminals for subscription television systems. In the past, many of the microprocessors of the subscriber terminals did not have the processing power to handle additional features. More importantly, the subscriber terminal is provided as a secure device which provides conditional access for the premium programming of the subscription service. An open architecture which would encourage a subscriber to open the outer cover of the terminal could be inimical to this security. Further, additional features generally require some change in the signals to or from the subscription service provider.

SUMMARY OF THE INVENTION

The invention provides a subscriber terminal with a plug-in expansion card. The expansion card is used to provide additional memory space, and renewed or additional security.

In the illustrated implementation, the expansion board is electrically connected to the memory bus of the control microprocessor. In this manner, any memory or additional processor mounted on the expansion board will be part of the memory space of the control microprocessor of the subscriber terminal. The additional memory, in the preferred embodiment, is Flash EPROM, but could as easily be ROM, or any of the different types of RAM including DRAM or the like. In addition, a secure microprocessor bus is included in the expansion space to allow the security apparatus of the subscriber terminal to be upgraded, changed or renewed.

Preferably, the expansion card includes a printed circuit board with edge connector terminals which plug into a standard circuit board connector. The connector is mounted internally to the subscriber terminal outer cover and the circuit board in a protective case enters the outer cover through a slot. The case is slideably received in the slot and a carrier with guides which direct the terminal end of the expansion board into the connector. The expansion board case is fitted with a hinged door at the terminal end of the board. The door is spring loaded to close the terminal end of the expansion board and protect the board from environmental hazards. The door in its dosed position rests on the surface of one of the sides of the expansion board to lower the profile of the expansion module. The low profile of the expansion module case allows a very narrow slot which is more secure than a larger opening.

As the expansion card case is inserted into the terminal cover slot, the carrier has a means for opening the door to expose the terminal end of the expansion board and allow for insertion into the connector. The case of the expansion board also has an integral upraised grip. The grip is used in combination with a recess in the cover of the subscriber terminal to facilitate removal from the connector. The grip and recess form a finger hold where the hand of the subscriber board may be placed to pull the expansion board from the connector and slot.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and aspects of the invention will be more clearly understood and better described if the following detailed description is read in conjunction with the appended drawings wherein:

FIG. 1 is a system block diagram of a subscription television system of the CATV type which includes a multiplicity of subscriber terminals;

FIGS. 2A and 2B is a detailed block diagram of one of the subscriber terminals of the system illustrated in FIG. 1;

FIGS. 3A-3D are pictorial representations of several download program code parameters transactions which the system uses to request the downloading of new program code to the subscriber terminal illustrated in FIG. 2;

FIG. 4 is a pictorial representation of the download program code transaction which the system uses to download program code which will supplement or replace program code in the memory space of the subscriber terminal illustrated in FIG. 2;

FIG. 5 is a detailed electrical schematic diagram of the memory architecture of the subscriber terminal illustrated in FIG. 2;

FIG. 6 is a detailed memory map of the memory space created by the architecture illustrated in FIG. 5;

FIG. 7 is a pictorial representation of the separation of internal and external memory for the subscriber terminal illustrated in FIG. 2;

FIGS. 8A and 8B are a detailed flow chart of the boot program stored in the internal ROM of the control microprocessor of the subscriber terminal illustrated in FIG. 2;

FIG. 9 is a detailed flow chart of the program code which stores the download program code parameters transactions for the subscriber terminal illustrated in FIG. 2;

FIG. 10 is a detailed flow chart of the program code which the control microprocessor executes in the off mode of the subscriber terminal illustrated in FIG. 2;

FIG. 11A is a perspective front view of the expansion card 138 illustrated in FIG. 2 with its protective door closed;

FIG. 11B is a perspective front view of the expansion card 138 illustrated in FIG. 2, with its protective door open;

FIG. 12 is a perspective pictorial of the subscriber terminal 40 receiving an expansion card 138 in accordance with the invention; and

FIGS. 12A-12C are fragmented side perspective views of the subscriber terminal illustrated in FIG. 12 with a snap on cover protecting the expansion slot of the terminal, with the slot open, and the expansion card inserted in the slot;

FIGS. 13A and 13B are fragmentary side views, shown partially cross-sectioned, of the expansion card partially inserted and fully inserted in the carrier of the subscriber terminal shown in FIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A subscription television system of the CATV type is more fully illustrated in FIG. 1. The subscription television system includes a headend 10 and a plurality of subscriber terminals 40, 44 and 48 which are connected over a distribution system 52. As is conventional, the distribution system 52 may include coaxial or optical fiber cable, system amplifiers, line extenders, etc. The headend 10 is under the supervision of a system manager 12 which controls a hardware controller, headend controller 22. A billing computer 11 communicates with the system manager 12 to authorize and transmit transactions to subscribers.

The television or other programming for the subscription system may come from a satellite downlink where it is decoded and demodulated by satellite receivers 18 into a number of channels. Each channel is either applied to a modulator 24 and 30 or a scrambler and modulator 26 and 28 which, under the control of the headend controller 22, remodulates the channels to the frequencies of the local subscription system channel line up. For a premium or restricted channel service (tiered, pay-per-view, or the like), some channels are scrambled by any of the known CATV methods by the scramblers and modulators 26 and 28, while the other channels can be transmitted without conversion. The program channels are then frequency division multiplexed onto the distribution system 52 by an RF combiner 34 as a broadband television signal. The plurality of channels of programming can then be transmitted over the distribution system 52 and supplied to each of the subscriber terminals 40, 44, and 48.

The scramblers and modulators 26 and 28 further may include the function of data insertion for its particular channel. This method of providing the data within the channel signal is generally termed in-band signaling. The data may be applied to any audio portion, video portion or both audio and video portions in combination, or any other portion of the television channel. Many subscription television systems have amplitude modulated data pulses on the audio subcarrier. Further, in other subscription television systems, data may be inserted into the vertical and/or horizontal blanking intervals of the video portion.

The data which is inserted into the television channel in this manner can be conditional access data to globally or locally address and control the subscriber terminals 40, 44 and 48, on screen text data, or other types of information from the headend controller 22. Other data and information, such as electronic program guides and information services, can be inserted into the channels from a data controller 20. The data controller 20 can receive local data or national data from the satellite downlink through the satellite receiver 18.

In addition, data can be transmitted over the distribution system 52 by out-of-band signaling. In this mode, the system manager 12 accesses an addressable transmitter 32 with transactions to transmit this data. The addressable transmitter 32 may be used to modulate a data signal on a frequency not associated with the television programming. The broadband television programming of the cable systems has generally been applied from 50 MHz to 550 MHz and above, while out-of-band signaling systems have been used in non-video portions of these signals, such as at 108.2 MHz with a frequency shift keying modulation technique. These transactions are combined with the broadband television signal at 36 and transmitted to the subscriber terminals 40, 44 and 48.

Transactions in the system are designated as addressed (to a particular subscriber terminal or group of subscriber terminals) and global (to all subscriber terminals). These transactions are in a standardized format which can be sent over any of the communication paths mentioned.

Signaling and data information may also flow in the reverse direction from the subscriber terminals to the headend via a reverse signaling path through the distribution system 52. In one form, the reverse signals are digital biphase shift keying (BPSK) modulated and applied to a frequency below 50 MHz. The signals flow back from the subscriber terminals to an IPPV processor where they are decoded. In addition, any of the subscriber terminals 40, 44 and 48 may include a modem and telephone link 56 to a telephone processor 16 at the headend 10. The information from processors 14 and 16 are directed to the system manager 12, which communicates to the billing computer 11 to obtain authorization and billing information. The reverse signaling system has generally been used for ordering pay-per-view (PPV) or impulse-pay-per-view (IPPV) events. In the future the reverse signal path may be used for any number of additional interactive services.

Referring to FIGS. 2A and 2B a detailed block diagram of one of the subscriber terminals, for example, the one indicated as 40 of the subscription television system will now be described. The broadband television signal from signal distribution system 52 is received at the input of up/down converter or tuner 100. An out-of-band data receiver 150 is also coupled to the broadband input. Conventionally, the up/down converter 100 may include an input filter, such as a diplexer, to separate the 108.2 MHz out-of-band signal and the broadband television signal. The up/down converter 100 can be tuned to a predetermined channel for receiving in-band video and audio data when not in use. The channel may be predetermined from the system manager 12 and, by one of the data transmission methods described herein, the predetermined channel identification can be stored in subscriber terminal 40.

When in use, the up/down converter 100 is tuned according to a channel entered by a subscriber via a user interface having an IR receiver 124, remote control 126 and terminal keypad 122. Up/down converter 100 uses a phase locked loop under the control of a tuning control 102 to convert the selected or predetermined default RF channel signal to a 45.75 MHz intermediate frequency signal. A multifunction control circuit (MCC) 104, preferably an application specific integrated circuit (ASIC) combining many subscriber terminal control and data handling functions into a single package, is linked to up/down converter 100 by a bidirectional link to the tuner control 102. The link has one path for tuning and a return link for feedback control of the tuning process. A feedback signal for automatic gain control and one for automatic frequency control are transmitted to the up/down converter 100 through filters 101, 103, respectively from a video demodulator 109.

A filter, such as a SAW filter 106, filters the IF channel signal to split the signal into separate video and audio portions for further processing. The video portion is demodulated and descrambled by the video demodulator 109 under the control of a descrambler control 110 of the MCC 104. The video demodulator 109 performs the sync restoration (descrambling of the video signal) for sync suppression scrambling. The video signal then passes through a band pass filter 130 and to a video inverter 132 where inverse video inversion (descrambling) takes place. The descrambling of the video portion, whether sync suppression, sync inversion, video line inversion, etc. is under the control of the descrambler control 110 of the MCC 104. The descrambler control 110 provides the necessary timing signals, inversion axis levels, and whether the video is inverted or not to the video inverter 132 and supplies the necessary timing, restoration levels and identification of sync pulses to be restored to the demodulator 109. The descrambler control 110 usually receives such descrambling information from pulses as in-band audio data.

In the other path, the audio signal is converted from the 41.25 MHz IF carrier to the intermodulation frequency of 4.5 MHz by a synchronous detector 105. Feedback for automatic gain control of detector 105 is supplied from the output of band pass filter 131. The audio signal may then be demodulated by an FM demodulator 119. An amplitude modulation detector 111 performs pulse detection to recover the in-band audio data which are amplitude modulated onto the audio carrier. The recovered in-band pulses are supplied to an in-band audio data decoder 117 of MCC 104 for processing after being shaped by pulse shaper 115. The in-band data, except for descrambling data, is stored in DRAM 137 for buffering. Descrambler control 104 accesses descrambling data directly for the video descrambling operation. Volume control of the audio signal is performed under the control of a volume control 118 of the MCC 104 and the microprocessor 128 as described in U.S. Pat. No. 5,054,071, incorporated herein by reference. After volume control, the audio signal is passed through a low pass filter 123 and a mute switch 125. The output of the mute switch 125 is applied to a modulator 142.

The MCC 104 receives the video signal after demodulation and descrambling and strips the in-band video data from the VBI of the signal with a VBI decoder 129. The in-band video data is transmitted at a frequency on the order of known teletext systems, such as about 4.0 megabits per second, and a data clock provides an appropriate sampling frequency higher than the Nyquist rate according to well known techniques. The in-band decoder 129 stores the data in DRAM 137 prior to processing by the microprocessor 128, the DRAM 128 serving as a data buffer.

The output of video inversion circuit 132 is also supplied to an on screen display control 127 of the MCC 104. The on screen display control 127 selectively generates on screen character and graphic displays in place of or overlaid on the video signal. The modulator 142 combines the video signal from the output of the on screen display control 127 and the audio signal from the output of the mute circuit 125 and converts the combined signal to the channel frequency selected by the microprocessor 128, such as channel 3/4 for NTSC. The combined and remodulated signal is supplied as an RF output to a television receiver in well known manner.

A control microprocessor 128 controls the overall operation of the subscriber terminal 40. The subscriber communicates to and controls the microprocessor 128 through an interactive user interface with an on screen display. The user interface includes a keyboard 122 on the front panel of the subscriber terminal 40 and the remote 126 which generate subscriber control signals for channel tuning, volume level control, feature selection, and the like. These subscriber control commands are decoded by an input scanner and control 148 of MCC 104. The remote IR receiver 124 of the user interface receives the commands from the infrared (IR) or other remote control 126, as is well known in the art, and provides commands to the microprocessor 128. The user interface additionally includes a 4 digit, 7 segment LED display 120 which displays the tuned channel numbers and diagnostics.

When the keypad 122 or IR remote control 126 is utilized to select a command, the microprocessor 128 operates to execute the command. For example, this operation may be to instruct the tuner control 102 to appropriately control up/down converter 100 to tune a selected channel. The subscriber terminal interacts with the subscriber by providing numerous on screen displays which assist in the operation of the terminal. The on screen displays provide information and prompts to guide the subscriber through many of the complex features of the terminal.

The descrambler control 110 of the MCC 104 utilizes recovered descrambling data to generate appropriate control signals, for example, inversion control and equalizing, sync restoration or regeneration for descrambling, or otherwise restoring the input baseband television signal. A secure microprocessor 136 determines whether the descrambler control 110 of MCC 104 carries out descrambling on a particular channel or what form of descrambling is required at a particular time by interpreting the authorization and control data downloaded from the system manager 12 (by any of the three data transmission schemes discussed herein, out-of-band, in-band audio or in-band video) into the internal NVM memory of the device. The non-volatile memory (NVM) in the secure microprocessor 136 stores secure data, for example, authorization data, scrambled channel data, scrambling mode data, some terminal configuration data and other required data.

The control microprocessor 128 operates by running a control program which preferably is partially stored in a read-only memory internal to the processor and partially stored in a non-volatile memory such as Flash EPROM memory 134. In addition, the control program of the control microprocessor 128 may also reside in the non-volatile memory of an expansion card 138. The microprocessor 128 communicates with the non-volatile memory 134 and 138 via a memory bus 141 which has data, address, and control lines. In addition, the microprocessor 128 controls the data decoders 117, 129 and 146 and the tuner control 102, volume control 118, on-screen display control 127, descrambler control 110 and input key scanner and control 148 via commands through MCC 104 and control microprocessor bus (CMB) 131. The microprocessor 128 also directly controls the mute switch 125 and the output frequency selection of the modulator 142. The microprocessor 128 includes additional capacity for other auxiliary device communications and control through a data port 140.

The memory control 112 permits data coming from the three data decoders 117, 129 and 146 to be placed in a volatile memory such as DRAM 137. There it can be accessed by the control microprocessor 128 via the CMB 131. The MCC 104 also distributes control instructions from the control microprocessor 128 to the other parts of the MCC 104 to provide operation of the rest of the subscriber terminal 40. The MCC 104 additionally connects to a secure microprocessor bus (SMB) 143 which permits communications between the secure microprocessor 136 and other portions of the subscriber terminal 40. The SMB 143 is further coupled to the expansion card 138 to provide renewable security.

The memory control 112 and microprocessor interfaces of the MCC 104 are the central communications facility for the control microprocessor 128 and the secure microprocessor 136. The memory control 112 receives requests to write to memory or read from memory from the microprocessors 128, 136 and the other controls and data decoders. It resolves contentions for memory transfers, giving priority to real time applications and the