SAA5244

The SAA5244 is a complete teletext decoder chip with built-in single page memory. It was introduced in March 1996 and was used in TVs and, more recently, Nathan Dane's Teletext In Vison Decoder.

Capabilites

The SAA5244 decodes teletext to Level 1 specifications.

It can decode additional packets such as Packets 8/30 and 27, making it compatible with FASTEXT, BSDP and PDC. It also automatically decodes the Hamming 8/4 error protection on these packets.

It's available as a 40-pin DIP or 44-pin QFP and requires a 27MHz clock signal, which can be supplied by a standard crystal with additional circuitry or a crystal oscillator.

It comes with 5 national options (additional characters) built-in, English, German, Swedish, Italian and French - and also 32 characters for OSD use.

The SAA5244 can act as a master or slave for video sync - it can even sync to 525 line sources for stable text overlay.

The chip can be used as a simple display chip, by setting it to master sync mode and disabling the acquisition circuits you can write freely to any point on the 25 row, 40 column display.

Programming/control

The SAA5244 is programmed via its I2C bus similarly to many other such chips of the era - a guide to the programming can be found (link) or in its datasheet.

I/O

The SAA5244 takes a standard 625 line Composite PAL video signal as its video input. This connects to pin 8 (DIP) or 25 (QFP) via a decoupling ceramic capacitor.

It outputs an RGB video signal, whose voltage peak can be controlled by the RGBREF pin, along with a Blanking signal which can be used to overlay text on a live video signal - this requires a SCART socket or additional circuitry. In master sync mode it outputs a sync signal from pin 12 (DIP) or 29 (QFP). In slave mode this pin is used as a sync input.

Additionally, the chip outputs an Odd/Even field clock, Y (luma) and a "contrast reduction" output for overlay use.