Altera DE2-115 User Manual download pdf (Page 52)

EX_IO[3] PIN_H14 Extended IO[3] 3.3V

EX_IO[4] PIN_F14 Extended IO[4] 3.3V

EX_IO[5] PIN_E10 Extended IO[5] 3.3V

EX_IO[6] PIN_D9 Extended IO[6] 3.3V

The DE2-115 board includes a 15-pin D-SUB connector for VGA output. The VGA synchronization

signals are provided directly from the Cyclone IV E FPGA, and the Analog Devices ADV7123

triple 10-bit high-speed video DAC (only the higher 8-bits are used) is used to produce the analog

data signals (red, green, and blue). It could support the SXGA standard (1280*1024) with a

bandwidth of 100MHz. Figure 4-21 gives the associated schematic.

Figure 4-21 Connections between FPGA and VGA

The timing specification for VGA synchronization and RGB (red, green, blue) data can be found on

various educational website (for example, search for “VGA signal timing”). Figure 4-22 illustrates

the basic timing requirements for each row (horizontal) that is displayed on a VGA monitor. An

active-low pulse of specific duration (time (a) 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) output to 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 similar as shown in Figure 4-22, 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 4-14 and Table 4-15 show different resolutions and durations of time periods a, b, c, and d

for both horizontal and vertical timing.

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Altera DE2-115 User Manual Page 52