8 vga port – Digilent 410-274P-KIT User Manual

Page 13

Nexys4™ FPGA Board Reference Manual

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8 VGA Port

The Nexys4 board uses 14 FPGA signals to create a VGA port with 4 bits-per-color and the two standard sync
signals (HS – Horizontal Sync, and VS – Vertical Sync). The color signals use resistor-divider circuits that work in
conjunction with the 75-ohm termination resistance of the VGA display to create 16 signal levels each on the red,
green, and blue VGA signals. This circuit, shown in Fig 11, produces video color signals that proceed in equal
increments between 0V (fully off) and 0.7V (fully on). Using this circuit, 4096 different colors can be displayed, one
for each unique 12-bit pattern. A video controller circuit must be created in the FPGA to drive the sync and color
signals with the correct timing in order to produce a working display system.

Command

Action

Set stream mode. The mouse responds with "acknowledge" (0xFA) then resets its movement
counters and enters stream mode.

Enable data reporting. The mouse responds with "acknowledge" (0xFA) then enables data
reporting and resets its movement counters. This command only affects behavior in stream
mode. Once issued, mouse movement will automatically generate a data packet.

Disable data reporting. The mouse responds with "acknowledge" (0xFA) then disables data
reporting and resets its movement counters.

Set mouse sample rate. The mouse responds with "acknowledge" (0xFA) then reads one more
byte from the host. This byte is then saved as the new sample rate, and a new “acknowledge”
packet is issued.

Resend. FE directs mouse to re-send last packet.

Reset. The mouse responds with "acknowledge" (0xFA) then enters reset mode.

Table 5. Microsoft Intellimouse-type extensions, commands and actions