Digilent 410-126P - Manual

D D i i g g i i l l e e n n t t P P m m o o d d S S S S D D ™ ™ P P e e r r i i p p h h e e r r a a l l M M o o d d u u l l e e
B B o o a a r r d d R R e e f f e e r r e e n n c c e e M M a a n n u u a a l l
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w w w . d ig i l en t inc . c om
Revision: March 6, 2007
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Overview
The PmodSSD offers a single two-digit seven-
segment display device (7sd) that can attach
directly to any Digilent system board. The 7sd
uses high-bright LEDs that can are easily
readable with less than 5mA of current, so they
can be driven directly from most system
boards.
Features include:
• two high bright seven-segment displays
• a 6-pin system connector
•
small form factor (0.80” x 0.80”).
Functional Description
The two digits on the common cathode seven-
segment LED display are each composed of
seven segments arranged in a “figure 8”
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 cathodes of the seven LEDs forming each
digit are tied together into one “common
cathode” circuit node, but the LED anodes
remain separate. The common cathode signals
are available as two “digit enable” input signals
to the display. The anodes of similar segments
on both digits are connected into seven circuit
nodes that are available from the Pmod
connector pins (so, for example, the two “D”
anode signals from the two digits are
connected to the P4 pin on J1). These seven
anode signals are available as inputs to the 2-
digit display. This signal connection scheme
creates a multiplexed display, where the anode
signals are common to both 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 the
display. This circuit drives the anode signals
and corresponding cathode patterns of each
Seven-Segment Display Connection Diagram
P1
P2
P3
P4
AA1
AB1
AC1
AD1
AE1
AF1
AG1
C1
AA2
AB2
AC2
AD2
AE2
AF2
AG2
C2
GND
Vcc
AE
AF
AG
C
GND
Vcc
560
AA
AB
AC
AD
P1
P2
P3
P4
GND
Vcc