Sigma DE2-70 manual Using VGA

DE2-70 User Manual

5.7 Using VGA

The DE2-70 board includes a 16-pin D-SUB connector for VGA output. The VGA synchronization signals are provided directly from the Cyclone II 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). The associated schematic is given in Figure 5.12 and can support resolutions of up to 1600 x 1200 pixels, at 100 MHz.

VGA_R[0..9]
VGA_G[0..9]
VGA_B[0..9]
VGA_G0	1
VGA_G1	2
VGA_G2	3
VGA_G3	4
VGA_G4	5
VGA_G5	6
VGA_G6	7
VGA_G7	8
VGA_G8	9
VGA_G9	10
VGA_BLANK_n	11
VGA_SYNC_n	12

9R_ _ A

8R A

_

7R A

_

6R A

_

5R A

_

4R A

_

3R A

_

2R A

_

1R A

_

0R A

R80

GV

GV

GV

GV

GV

GV

GV

GV

GV

GV

R81

RSET

U10

48

47

46

45

44

43

42

41

40

39

38

37

9R 8R 7R 6R 5R 4R 3R 2R 1R 0R

EVA TES S R

P

36

G0

VREF

35

G1

COMP

34

G2

IOR

33

G3

IOR

32

G4

IOG

31

G5

ADV7123

IOG

30

G6

VAA

29

G7

VAA

28

G8

IOB

27

G9

IOB

26

BLANK

GND

25

SYNC

GND

KC

AA 0 1 2 3 4 5 6 7 8 9 LOC V B B B B B B B B B B

13

14

15

16

17

18

19

20

21

22

23

24

0B

1B

2B

3B

4B

5B

6B

7B

8B

9B

KCLO C

_AG V

_AG V

_AG V

_AG V

_AG V

_AG V

_AG V

_AG V

_AG V

_AG V

_AG V

VGA_VCC33
4.7K
560
BC47	BC48
0.1u	0.1u
				VGA_R
				VGA_G
				VGA_B
VGA_VCC33	R82	R83	R84
	75	75	75
		VGA_HS		R85	47
		VGA_VS		R86	47

	J7
	1
	2
	3
	4
	5
	6
	7
	8
	9
	10
	11
	12
	13
	14
	15
BC49	0.1u

1

5 16

6

11

10

15 VGA

17

VGA_VCC33

Figure 5.12. VGA circuit schematic.

The timing specification for VGA synchronization and RGB (red, green, blue) data can be found on various educational web sites (for example, search for “VGA signal timing”). Figure 5.13 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) 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 5.13, 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 5.9 and

5.10show, for different resolutions, the durations of time periods a, b, c, and d for both horizontal and vertical timing.

Detailed information for using the ADV7123 video DAC is available in its datasheet, which can be

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