Specifications

CHAPTER 4
Expansion Features
58 The DAV Connector
Using the YUV Bus 4
The video input module contains a digital video decoder and scaler (DESC), the Philips
SAA7140 IC. Logic on the video input card uses the CVBS port on the DESC and pulls
the FLD signal low, disabling the YUV bus. For an expansion card to use the YUV bus,
the software associated with the card must set the FLD signal high so that the DESC will
accept data on the YUV bus. To do that, the software can use the Cuda Dispatch
Manager to issue a IIC command to write to register $E of the DESC. For information
about using the registers in the DESC IC, please refer to the SAA7140 Philips Desktop
Video Handbook.
Video Data Format 4
Digital video data is transmitted as lines and fields. Each line consists of an even number
of samples on the Y and UV buses as shown in Figure 4-5. HREF is high during a video
line and low during the horizontal blanking interval. The falling edge of the VS signal
indicates the beginning of a video field. For more information about digital video data in
YUV format, see the Power Macintosh DAV Interface for PCI Expansion Cards Developer
Note.
Input current drain ± 20 µA
Output voltage low 0.4 V
Output voltage high 3.5 V
Output current ± 400 µA
Table 4-11 DAV signal levels (continued)
Specification Minimum Maximum