410-345 (DIGILENT)

The 410-345 from Digilent is a Pmod VGA (video graphics array). The Pmod VGA provides a VGA port to any board with Pmod connectivity. The host board must be capable of driving a fast parallel data bus in order to properly drive a display with the Pmod VGA. The Pmod VGA uses 14 input pins to create an analogue VGA output port. This translates to 12bit colour depth and two standard sync signals (horizontal sync (HS) and vertical sync (VS)). The digital to analogue conversion is done using a simple R-2R resistor ladder. The ladder works in conjunction with the 75ohm termination resistance of VGA display to create 16 analogue signal levels for the red, blue and green VGA signals. This circuit produces video colour signals that proceed in equal increments between 0V (fully off) and 0.7V (fully on). With 4bit each for red, blue and green, 4096 (16 x 16 x 16) different colours can be displayed, one for each unique 12bit pattern.