Digilent Atlys Manuale di riferimento - Pagina 16

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Atlys Reference Manual

contain movement data as shown in the figure above. Data is valid at the falling edge of the clock, and

the clock period is 20 to 30KHz.

The mouse assumes a relative coordinate system wherein moving the mouse to the right generates a

positive number in the X field, and moving to the left generates a negative number. Likewise, moving

the mouse up generates a positive number in the Y field, and moving down represents a negative

number (the XS and YS bits in the status byte are the sign bits – a '1' indicates a negative number).

The magnitude of the X and Y numbers represent the rate of mouse movement – the larger the

number, the faster the mouse is moving (the XV and YV bits in the status byte are movement overflow

indicators – a '1' means overflow has occurred). If the mouse moves continuously, the 33-bit

transmissions are repeated every 50ms or so. The L and R fields in the status byte indicate Left and

Right button presses (a '1' indicates the button is being pressed).

Basic I/O

The Atlys board includes six pushbuttons, eight slide switches, and eight LEDs for basic digital input

and output. One pushbutton has a red plunger and is labeled "reset" on the PCB silkscreen – this

button is no different than the other five, but it can be used as a reset input to processor systems. The

buttons and slide switches are connected to the FPGA via series resistors to prevent damage from

inadvertent short circuits. The high efficiency LED anodes are connected to the FPGA via 390-ohm

resistors, and they will brightly illuminate with about 1mA of current when a logic high voltage is

applied to their respective I/O pin.

Doc: 502-178

Mouse Data Format

Pushbuttons

BTNU: N4

BTNC: F5

BTNR: F6

BTNL: P4

BTND: P3

BRST: T15

Slide Switches

LEDs

SW0: A10

LD0: U18

SW1: D14

LD1: M14

SW2: C14

LD2: N14

SW3: P15

LD3: L14

SW4: P12

LD4: M13

SW5: R5

LD5: D4

SW6: T5

LD6: P16

SW7: E4

LD7: N12

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