STMicroelectronics Reveals Chipset Used in Hot Set-Top Boxes
Following British Sky Broadcasting's (BSkyB) launch of the United Kingdom's first digital TV service late last year--and with 350,000 British subscribers already on-line and paying--silicon maker STMicroelectronics (ST; Lexington, MA) has now revealed the details of the chipset that lies at the heart of BSkyB's SkyDigital set-top boxes (STBs). All of the "digiboxes" manufactured to date for the SkyDigital service include the core ST chipset, of which more than 600,000 units were shipped to STB OEMs last year. The ICs are now going to be available to OEMs.
According to ST, the integrated News Digital Systems (NDS) Conditional Access Module makes the ICs particularly suitable for the BSkyB application, but the company is quick to point out that the chips can also be used in virtually any and all digital broadcast applications. In addition to the silicon, ST also provides supporting software, including device drivers and a realtime kernel for use with OpenTV middleware chosen by BSkyB. If you're designing an STB, this is a one-stop shop.
Close Collaboration
The chipset is the result of a close collaboration between Service Operator BSkyB, OEMs, and ST. Silicon includes the ST20-TP3, an MPEG2 transport demultiplexer with Embedded Conditional Access (ICAM) and a 32-bit RISC CPU. The STi3520L device is an MPEG2 audio/video Decoder with display features that support e-commerce and interactivity. The STV0119 is a PAL/NTSC video encoder. It works in conjunction with an STV0199 link/tuner interface, an ST7 front panel microcontroller, and various serial EEPROMs and flash memories.
The ST20-TP3 is a variant of the industry standard ST20-TPx family that combines the functions of the STB transport IC and system microcontroller into a single package. The performance offered by the ST20 32-bit RISC core permits device drivers and synchronization, and system management functions, as well as electronic program guide and user interfaces to be performed in software. Code also handles conditional access control and the interpretation and execution of downloadable application programs.
Variable Length Instructions
The system's use of a variable length instruction format also leads to high code density, slashing the cost of program memory. ST claims the performance of the processor can also be exploited by a STB manufacturer to offer superior quality on-screen graphics, program guides and other nifty user interfaces.
ST says its 5O MHz, 32-bit RISC core was also engineered to reduce system cost--especially for high volume applications. Notable features include an integral hardware micro kernel with multi-priority process scheduling, trap/exception handling, DMA, interrupt and timer support, and fast context switching.
A fully integrated memory/cache subsystem includes simultaneously accessible instruction and data caches. A separate four Kbyte SRAM can be used to store on-chip data, stack data or code for time-critical routines. Peripherals include a programmable external memory interface, DMA engines, and interrupt, diagnostic and low power controllers. Of course, there are a variety of parallel and serial I/0 ports. There's also teletext and smartcard interfaces, as well as the usual assortment of counters and timers.
It's Testable
To ensure testability, which is always a major cost concern for OEMs, ST has included a JTAG access port. To support interactive services, the chip incorporates both IEEE-1284 and IEEE-1394 (FireWire) interfaces too.
The ST3520L MPEG Audio/MPEG-2 Video Decoder is based on the STi3520 architecture that's already used in millions of STBs worldwide for DVB or DSS programs. In addition, the STi3520L offers advanced graphics features to support interactive services and program guides and menus. New features include eight-bit graphics with improved filtering, a letter box format for display of 16/9 pictures and video up/down scaling, as well as the ability to simultaneous display three picture planes (OSD, MPEG video, and a still video backdrop).
Want more information? Contact STMicroelectronics, Inc., 10 Maguire Rd., Bldg. One, 3rd Floor, Lexington, MA 02421. Phone: (781) 861-2650. Fax: (781) 861-2678.