Digital television decoder

1. A method of operating a digital television decoder, said decoder comprising a random access memory, said random access memory storing onboard software, wherein said decoder is operable in a run mode to execute said onboard software, said method comprising:

downloading a group of applications and data usable by said applications, said group of applications and data together forming a current interactivity image of the onboard software that is broadcast with audio-visual data;

activating a power saving mode on said decoder; and

upon activating said power saving mode:

maintaining power to said random access memory;

suspending execution of said onboard software;

acquiring an execution context of said onboard software;

updating said current interactivity image by downloading an updated interactivity image; and

saving said updated interactivity image and said execution context in said memory;

wherein said updated interactivity image and execution context is are saved in a data storage area of said random access memory, wherein properties of said data storage area are stored in a secure area of said random access memory, and wherein said secure area is addressed by a fixed address that remains unchanged even after a rebooting of said onboard software.

2. A method according to claim 1 , wherein execution of said onboard software remains suspended until said run mode is activated, and upon activation of said run mode: resuming execution of said onboard software using said updated interactivity image and execution context.

3. A method according to claim 1 , wherein if said run mode is activated prior to the end of updating said interactivity image, execution of said onboard software resumes using an interactivity image and execution context that were previously saved in said random access memory.

4. A method according to claim 1 , wherein properties of said context storage area are stored in a property storage area of said secure area, and wherein said property storage area comprises an address for said context storage area.

5. A method according to claim 4 , wherein said property storage area comprises a checksum that is computed for said context storage area.

6. A method according to claim 5 , wherein prior to suspending execution of said onboard software, said onboard software is rebooted, and following said rebooting of said onboard software said method further comprises:

recomputing a checksum for said context storage area; and comparing said recomputed checksum with said checksum stored in said property storage area of the secure area;

wherein if said recomputed checksum that is recomputed for said context storage area is the same as the checksum stored in said property storage area of said secure area, the execution context saved in said context storage area is used to run said onboard software.

7. A method according to claim 4 , wherein said property storage area stores information relating to type of data and size of memory allocated to said context storage area.

8. A method according to claim 1 , said decoder further comprising: an internal clock running at a clock rate; and other hardware, wherein activating said power saving mode comprises limiting said clock rate and shutting down hardware not critical for maintaining power to said random access memory.

9. A method according to claim 1 , wherein prior to suspending execution of said onboard software, said onboard software is rebooted.

10. A method according to claim 9 , wherein said onboard software is rebooted only if the time that has elapsed since said onboard software was previously rebooted exceeds a predetermined value.

11. A method according to claim 10 , further comprising measuring the time that has elapsed using a clock; and resetting the time to compensate for the reduction of the clock frequency while said decoder is in said power saving mode.

12. A method according to claim 11 , wherein said clock comprises an internal clock.

13. A method according to claim 11 , wherein said clock comprises an external clock.

14. A method according to claim 9 , wherein said onboard software is rebooted only if execution of said onboard software has been suspended a predetermined number of times.

15. A digital television decoder comprising:

a receiver downloading a group of applications and data usable by said application, said group of applications and data together forming an interactivity image of onboard software executable by said decoder in a run mode and broadcast with audio-visual data;

a random access memory, said random access memory storing said onboard software, said random access memory comprising:

a data storage area operable to store: an execution context acquired after execution of said onboard software is suspended; and an updated interactivity image downloaded after execution of said onboard software is suspended, following said decoder being placed in a power saving mode, and

a secure area addressable by a fixed address that remains unchanged even after a rebooting of said onboard software, wherein said secure area comprises property storage areas operable to store properties of said data storage area.

16. A digital television decoder comprising:

a receiver for downloading a group of applications and data usable by said application, said group of applications and data together forming an interactivity image of onboard software executable by said decoder in a run mode and broadcast with audio-visual data;

memory means for storing said onboard software, said memory means comprising:

data storage means for storing: an execution context acquired after execution of said onboard software is suspended; and an updated interactivity image downloaded after execution of said onboard software is suspended, following said digital television decoder being placed in a power saving mode; and

secure storage means for storing, wherein said secure storage means is addressable by a fixed address that remains unchanged even after a rebooting of said onboard software, and wherein said secure storage means comprises property storage means for storing properties of said data storage means.