1997-06-17 , E/IC-476/540

A wide range of information, ranging from video programming data to the latest share prices and up-to-the-minute newscasts, is now made available in the vertical blanking interval (VBI) of standard broadcast TV signals. Intel's revolutionary Intercast™ technology will even make it possible to transmit World Wide Web pages alongside TV programmes, allowing viewers to instantly access related information via an Internet connection.

To simplify the design of consumer products for this technology, Philips Semiconductors has introduced the  SAA5284 - a unique video data acquisition chip that greatly simplifies the recovery of VBI data from a TV signal so that it can be used in multimedia PCs and set-top boxes. In addition to recovering VBI data, the SAA5284 also captures the full-field (FF) data transmitted on specialist subscriber-TV channels.

"Over 20 years experience in world-wide Teletext decoding has enabled us to make the SAA5284 a true multi-standard solution that eliminates virtually all of the processor overhead currently needed for VBI and FF data recovery", commented Paul Martin, Philips Semiconductors' Product Marketing Manager for video data acquisition products.

The SAA5284 has an input multiplexer for two analog composite-video baseband signal (CVBS) sources, the selected input being digitized on-chip so that all signal filtering, clock recovery and data slicing can be performed entirely in the digital domain. Full programmability makes the SAA5284 a true multi-standard device, capable of decoding all known VBI formats including 525- and 625-line Teletext, Intercast™, wide-screen signalling, video programming system (VPS), closed captioning and PDC data broadcast standards. For accurate data recovery, the entire demodulation process has been optimized to eliminate the common types of distortion found in broadcast TV signals.

Packet filtering normally performed in software is performed on-chip in the SAA5284. This significantly reduces host processor overhead and allows this unique data acquisition chip to be used with low-cost microcontrollers as well as with high-performance CPUs. Packet data is buffered in on-chip RAM and output via an 8-bit parallel port that is compatible with both Intel and Motorola style processors. This port also has a 'video' mode which allows the host to access packet data over the same bus that carries YUV digital video data, making the SAA5284 an ideal companion IC for Philips Semiconductors' desk-top-video chip sets.

To produce a complete ISA-bus video data acquisition card the SAA5284 requires little more than the addition of an address decoding chip. Used in conjunction with Philips Semiconductors'  SAA7146 PCI-bus bridge IC it provides a 2-chip solution for PCI-bus video data acquisition cards. In set-top box applications the SAA5284 can optionally be controlled via the I²C-bus.

Recognising that software is as important as hardware in shortening its customers' time-to-market, Philips Semiconductors has developed both link layer (DLL) and register-level (VxD) driver software modules for the SAA5284. These modules, which are available under license, allow designers to develop products for a wide range of data broadcasting applications without the need for specialist Teletext or VBI knowledge.

The SAA5284 is a 5-volt device packaged in a 44-lead quad flat pack that is optimised for good EMC performance.

Philips Semiconductors, a division of Philips Electronics NV, headquartered in Eindhoven, The Netherlands, is the ninth largest semiconductor supplier in the world. Philips Semiconductors' innovations in digital audio, video, and mobile technology position the company as a leader in the consumer, multimedia and wireless communications markets. Sales offices are located in all major markets around the world and are supported by regional customer application labs.