Altera LCD Multimedia HSMC - Manual (Page 34)

Altera Corporation 2–26
August 2008 LCD Multimedia HSMC
Board Components and Interfaces
■ output + HS, VS, and FIELD
■ Applications: DVD recorders, LCD TV, Set-top boxes, Digital TV
■ Portable video devices
VGA DAC Interface
The board includes an Analog Devices ADV7123 VGA DAC and 16-pin
D-SUB connector for VGA output.
Table 2–19 below lists VGA DAC
Interface board reference and manufacturing information.
The VGA DAC interface features:
■ 240-MHz triple 10-bit high-speed video DAC
■ 15-pin high-density D-sub connector
The VGA synchronization signals are provided directly from the Cyclone
III FPGA, and the Analog Devices ADV7123 triple 10-bit high-speed
video DAC is used to produce the analog data signals (red, green, and
blue).
Figure 2–15 illustrates the basic timing requirements for each row
(horizontal) that is displayed on a VGA monitor. An active-low pulse of
specific duration (time) as shown in the figure is applied to the horizontal
synchronization (hsync) input of the monitor, which signifies the end of
one row of data and the start of the next. The data (RGB) inputs on the
monitor must be off (driven to 0 V) for a time period called the back porch
(b) after the hsync pulse occurs, which is followed by the display interval
(c). During the data display interval, the RGB data drives each pixel in
turn across the row being displayed. Finally, there is a time period called
the front porch (d) where the RGB signals must again be off before the
next hsync pulse can occur. The timing of the vertical synchronization
(vsync) is the same as shown in
Figure 2–15 , except that a vsync pulse
signifies the end of one frame and the start of the next, and the data refers
to the set of rows in the frame (horizontal timing).
Table 2–20 and
Table 2–21 show, for different resolutions, the durations of time periods a,
b, c, and d for both horizontal and vertical timing.
Table 2–19. VGA Output DAC
Board Reference Device Description Manufacturer
Manufacturer Part
Number
Manufacturer
Website
U9 240 MHz Triple 10-
Bit High Speed Video
DAC Analog Devices ADV7123 www.analog.com