Digilent 410-258P-KIT - Manual (Page 14)

Anvyl Reference Manual
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configuration. VCO outputs have eight equally-spaced outputs (0º, 45º, 90º, 135º, 180º, 225º, 270º,
and 315º) that can be divided by any integer between 1 and 128.
Basic I/O
The Anvyl board includes fourteen LEDs (ten red, two yellow, and two green), eight slide switches,
eight DIP switches in two groups, four push buttons, three two-digit seven-segment displays, and a
630 tie-point breadboard with ten digital I/O’s. The push buttons, slide switches and DIP switches are
connected to the FPGA via series resistors to prevent damage from inadvertent short circuits (a short
circuit could occur if an FPGA pin assigned to a pushbutton or slide switch was inadvertently defined
as an output). The pushbuttons are "momentary" switches that normally generate a low output when
they are at rest, and a high output only when they are pressed. Slide switches and DIP switches
generate constant high or low inputs depending on their position. The ten digital breadboard I/O’s
(BB1 – BB10) are connected directly to the FPGA so that they can easily be incorporated into custom
circuits.
Push
Buttons
Slide
Switches
DIP
Switches LEDs Breadboard
BTN0: E6 SW0:V5 DIP8-1: G6 LD0:W3 LD9:R7 BB1: AB20 BB9:R19
BTN1: D5 SW1:U4 DIP8-2: G4 LD1:Y4 LD10:U6 BB2: P17 BB10:V19
BTN2: A3 SW2:V3 DIP8-3: F5 LD2:Y1 LD11:T8 BB3: P18
BTN3: AB9 SW3:P4 DIP8-4: E5 LD3:Y3 LD12:T7 BB4: Y19
SW4:R4 DIP9-1: F8 LD4:AB4 LD13:W4 BB5: Y20
SW5:P6 DIP9-2: F7 LD5:W1 LD14:U8 BB6: R15
SW6:P5 DIP9-3: C4 LD6:AB3 BB7: R16
SW7:P8 DIP9-4: D3 LD7:AA4 BB8: R17
Table 1. Basic I/O pinout.
Seven Segment Display
The Anvyl board contains three 2-digit common cathode seven-segment LED displays. Each of the
two digits is composed of seven segments arranged in a “figure eight” pattern, with an LED embedded
in each segment. Segment LEDs can be individually illuminated, so any one of 128 patterns can be
displayed on a digit by illuminating certain LED segments and leaving the others dark. Of these 128
possible patterns, the ten corresponding to the decimal digits are the most useful.
The common cathode signals are available as six “digit enable” input signals to the three 2-digit
displays. The anodes of similar segments on all six digits are connected into seven circuit nodes
labeled AA through AG (so, for example, the six “D” anodes from the six digits are grouped together
into a single circuit node called “AD”). These seven anode signals are available as inputs to the 2-digit
displays. This signal connection scheme creates a multiplexed display, where the anode signals are
common to all digits but they can only illuminate the segments of the digit whose corresponding
cathode signal is asserted.
A scanning display controller circuit can be used to show a two-digit number on each display. This
circuit drives the cathode signals and corresponding anode patterns of each digit in a repeating,
continuous succession, at an update rate that is faster than the human eye response. Each digit is
illuminated just one-sixth of the time, but because the eye cannot perceive the darkening of a digit
before it is illuminated again, the digit appears continuously illuminated. If the update (or “refresh”)
rate is slowed to a given point (around 45 hertz), then most people will begin to see the display flicker.