GENERAL DESCRIPTION
The SAA7146A, Multimedia PCI-bridge, is a highly integrated circuit for DeskTop Video (DTV) applications.
The device provides a number of interface ports that enable a wide variety of video and audio ICs to be connected to the PCI-bus thus supporting a number of video applications in a PC. One example of the application capabilities is shown in Fig.48.
Figure 1 shows the various interface ports and the main internal function blocks.

FEATURES
Video processing
• Full size, full speed video delivery to and from the frame buffer or virtual system memory enables various processing possibilities for any external PCI device
• Full bandwidth PCI-bus master write and read (up to 132 Mbytes/s)
• Virtual memory support (4 Mbytes per DMA channel)
• Processing of maximum 4095 active samples per line and maximum 4095 lines per frame
• Vanity picture (mirror) for video phone and video conferencing applications
• Video flip (upside down picture)
• Colour space conversion with gamma correction for different kinds of displays
• Chroma Key generation and utilization
• Pixel dithering for low resolution video output formats
• Brightness, contrast and saturation control
• Video and Vertical Blanking Interval (VBI) synchronized programming of internal registers with Register Programming Sequencer (RPS), ability to control two asynchronous data streams simultaneously
• Memory Management Unit (MMU) supports virtual demand paging memory management (Windows, Unix, etc.)
• Rectangular clipping of frame buffer areas minimizes PCI-bus load
• Random shape mask clipping protects selectable areas of frame buffer
• 3 × 128 Dword video FIFO with overflow detection and ‘graceful’ recovery.

Audio processing
• Time Slot List (TSL) processing for flexible control of audio frames up to 256 bits on 2 asynchronous bidirectional digital audio interfaces simultaneously (4 DMA channels)
• Video synchronous audio capture, e.g. for sound cards
• Various synchronization modes to support I2S-bus and other different audio and DSP data formats
• Audio input level monitoring enables peak control via software
• Programmable bit clock generation for master and slave applications.

Scaling
• Scaling of video pictures down to randomly sized windows (vertical down to 1 : 1024; horizontal down to 1 : 256)
• High Performance Scaler (HPS) offers two-dimensional, phase correct data processing for improved signal quality of scaled video data, especially for compression applications
• Horizontal and vertical FIR filters with up to 65 taps
• Horizontal upscaling (zoom) supports e.g. CCIR to square pixel conversion
• Additional Binary Ratio Scaler (BRS) supports CIF and QCIF formats, especially for video phone and video conferencing.

Interfacing
• Dual D1 (8-bit, CCIR 656) video I/O interface
• DMSD2 compatible (16-bit YUV) video input interface
• Supports various packed (pixel dithering) and planar video output formats
• Data Expansion Bus Interface (DEBI) for interfacing with e.g. MPEG or JPEG decoders with Intel (ISA like) and Motorola (68000 like) protocol style, capability for immediate and block mode (DMA) transfers with up to 23 Mbytes/s peak data rate
• 5 digital audio I/O ports
• 4 independent user configurable General Purpose I/O Ports (GPI/O) for interrupt and status processing
• PCI interface (release 2.1)
• I2C-bus interface (bus master).

General
• Subsystem (board) vendor ID support for board identification via software driver
• Internal arbitration control
• Diagnostic support and event analysis
• Programmable Vertical Blanking Interval (VBI) data region for e.g. to support INTERCAST, teletext, closed caption and similar applications
• 3.3 V supply enables reduced power consumption, 5 V tolerant I/Os for 5 V PCI signalling environment.