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www.digilentinc.com
Revision: 5/7/02 215 E Main Suite D | Pullman, WA 99163
(509) 334 6306 Voice and Fax
Overview
The Digilab Digital I/O board 2 (the DIO2) is
one of several expansion boards designed to
mate with Digilab system boards. The DIO2
board provides an assortment of frequently
used digital I/O devices, many of which are
controlled by an on-board Xilinx XC95108
CPLD. The CPLD also provides a bus interface
to simplify communications with Digilab
system boards. DIO2 boards can be combined
with Digilab system boards to implement
projects ranging from basic logic designs to
general computer systems, without the need for
any other components.
DIO2 board features include:
• A XC95108 CPLD for I/O device and
system bus control;
• A 16x2 character LCD with integral
Samsung controller IC;
• A four digit seven-segment LED display;
• 16 individual LEDs of various colors;
• An 8-bit VGA port;
• A 15-button keypad;
• 8 slide switches;
• A PS2 mouse/keyboard port;
• An on board 5VDC regulator.
The CPLD comes pre-configured with the
circuit shown in Appendix 1, but it can also be
reprogrammed from any Xilinx CAD tool,
including the free WebPack tools available
from the Xilinx website. CPLD configuration
can be accomplished using the Xilinx JTAG
cable or the Digilent XC95 programming
board.
16x2
LCD
15 LEDs
4 7-seg.
displays
8 switches
15 button
keypad
PS2
port
XC95108
PC84
10
VGA
port
5VDC
regulator
2
3
8
data
control
4
address
6
JTAG
4
Connector BConnector A
GND
VU
VDD
DIO2 circuit board block diagram
Digilab DIO2 Reference Manual Digilent, Inc.
www.digilentinc.com page 2 of 19
Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.
Functional description
The DIO2 board includes many frequently used peripheral devices found in digital systems, including
several output display devices and several input devices. When mated with a Digilab main board, the
DIO2 board provides a highly flexible digital system development platform. The DIO2 board centers
on a Xilinx XC95108 CPLD that provides a convenient interface to most of the I/O devices, as well as
a control bus between an attached system board and the I/O devices. Since the CPLD on the DOI2
board is user configurable, many different I/O control and communication schemes can easily be
implemented.
Although the DIO2 board has been designed as a peripheral board for various Digilab system boards, it
can also be used as a CPLD demonstration/development board. Digilent produces a low cost power
supply/programming board that can be connected to the DIO2 board to create a stand-alone, very low
cost CPLD platform. This board, called the DXC95 board, provides a JTAG programming interface, a
power supply, a clock source, and a small breadboard area (see www.digilentinc.com for more
information).
This document presents the
circuits, I/O devices, and
interfaces in the DIO2 board.
When needed, manufacturer part
numbers have been provided so
that further reference material
can be obtained from their
websites.
Signals
All named signals used on the
DIO2 board are defined in the
table on the right. Voltage levels
for all signals arriving from an
attached Digilab system board
are determined by the system
board, but all signals arising on
the I/O board derive from the
on-board 5VDC regulator (so
they are all 5V CMOS signals).
The DIO2 board uses a two-
layer process, so all signals are
available on the top and bottom
layers. Many signals are brought
to a test point header for easy
test and measurement equipment
attachment.
Power Supplies
VU Unregulated power supply voltage from attached system
board – typically 5-9VDC. Available only on J1 P40, this
supply is regulated to 5VDC to supply on onboard devices.
VDD* Regulated power supply voltage (5VDC) from on-board
regulator. This supply is used by all devices on DIO2 board.
GND* System ground
CPLD – system board bus signals
D7-D0* Bi-directional data bus between B connector and CPLD/LCD
A5-A0* Address lines to select locations in CPLD
CS* Chip select used for CPLD interface on DIO2 board
WE* Write enable for CPLD memory locations
OE* Output enable for CPLD data signals
BOCI* “Button Out-Clock In” pin, used as clock input to CPLD
LCD control signals
D7-D0 Data bus – same as CPLD data signals
LCD_RW* LCD Read/Write signal – ‘1’ for read mode
LCD_RS* LCD Register Select – ‘1’ for data register, ‘0’ for instruction
LCD_E LCD Enable signal – active high; falling edge latches data
VGA and PS2 signals (routed directly from B connector, not through CPLD)
HS* VGA Horizontal Sync signal
VS* VGA Vertical Sync signal
R1, R0* VGA 2-bit red data
G2-G0* VGA 3-bit green data
B2-B0* VGA 3-bit blue data
KCLK* PS2 (Keyboard or Mouse) clock signal
KDAT* PS2 (Keyboard or Mouse) data signal
On board devices (routed through CPLD)
BTN0-E Pushbuttons (A through E)
SW1-SW8 Slide switches (1 through 8)
LD0-LDF Discreet LEDs (0 through F)
CA-CF Seven-segment display cathodes
AN1-AN3 Seven-segment display anodes
* available on test point header
Table 1. DIO2 board signal definitions