Digilent DIO4 User Manual
Digilent Hardware
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Revision: August 11, 2004
215 E Main Suite D | Pullman, WA 99163
(509) 334 6306 Voice and Fax
Doc: 500-227
page 1 of 9
Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.
Overview
The DIO4 circuit board provides a low-cost,
ready-made source for many of the most
common I/O devices found in digital systems. It
can be attached to a Digilent system board to
create a circuit design platform capable of
hosting a wide array of circuits. DIO4 features
include:
• A 4-digit seven segment LED display;
• 8 individual LEDs;
• 4 pushbuttons;
• 8 slide switches;
• 3-bit VGA port;
• PS/2 mouse or keyboard port.
Functional Description
The DIO4 can be attached to Digilent system
boards to quickly and easily add several useful
I/O devices. The DIO4 draws power from the
system board, and signals from all I/O devices
are routed to individual pins on the system
board connectors. These features allow the
DIO4 to be incorporated into system-board
circuits with minimal effort.
All devices on the DIO4 use the 3.3V supply
from the system board, except for the PS/2
port which needs a 5VDC supply (the DIO4
contains a 5VDC regulator). Signals coming
from the PS/2 port are routed through level-
shifting buffers to protect system boards that
do not have 5V tolerant inputs.
Power Supplies
The DIO4 draws power from three pins on the
40-pin connectors: pin 37 supplies 3.3V; pin 39
provides system GND, and pin 40 supplies
unregulated voltage (VU). VU is connected to a
5VDC LDO regulator to produce a 5VDC supply
for the PS/2 interface. The 3.3V supply is used to
drive all other I/O devices on the board. The
DIO4 consumes 5-10mA from the VU supply,
and 10-50mA from the 3.3V supply (depending
on how many LEDs are illuminated).
Seven-Segment LED display
The DIO4 board contains a modular 4-digit,
common anode seven-segment LED display. In
a common anode display, the seven anodes of
the LEDs forming each digit are connected to
four common circuit nodes (labeled AN1 through
AN4 on the DIO4). Each anode, and therefore
each digit, can be independently turned on and
off by driving these signals to a ‘0’ (on) or a ‘1’
(off). The cathodes of similar segments on all
four displays are also connected together into
seven common circuit nodes labeled CA through
CG. Thus, each cathode for all four displays can
be turned on (‘0’) and off (‘1’) independently.
Connector P2
Connector P1
8 switches
4 buttons
8 LEDs
4 7-seg.
displays
PS2
Port
VGA
Port
Latch
Debounce
Buffer
DIO4 circuit board block diagram