This is the 'master controller' of the Digibox. Based around an ST20 RISC processor, this device offers high MIPS (millions of instructions per second) for a low power drain. Although it seems to respond slowly on this particular model, there is a lot of stuff going on in the background and the relatively slow clock speed shows just what this CPU is capable of.
This IC is not just a CPU. It also handles the demultiplexing of the video and audio streams (one satellite 'channel' hosts a boutique which may consist of five or six TV channels, fifty to sixty radio channels, or combinations of the two; demultiplexing is the process of extracting the stuff you want to see from all of the data available). Additionally, custom hardware included in the IC decrypts the MPEG data (if necessary) under the control of signals inserted in the data itself, and communications with the subscriber card.
Because of the close relationship with the CPU, it is not difficult to provide further controls which include 'authorising' the subscriber card and updating the EPG with new channels.
The OpenTV core, and possibly within various Digibox variants, supports several processors besides the ST20: ARM/StrongArm, MIPS, PowerPC, and the ever-popular 68000 series.
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Copyright © 2005 Richard Murray