Digilent X-Board - Manual (Page 5)

Digilent
X-Board Reference Manual
www.digilentinc.com
Copyright Digilent, Inc. Page 5/6 Doc: 502-107
6-pin header connectors
The X-Board provides eight 6-pin peripheral module connectors. Each connector provides V
DD
, GND,
and four unique CPLD signals.
Several 6-pin module boards that can attach to these connectors are available from Digilent, including
speaker boards, H-bridge boards, sensor boards, etc. Please see
www.digilentinc.com for more
information.
See the X-Board schematic for pin assignments.
Peripheral Modules
The kit includes three peripheral modules: PS/2, Switches, and a dual Seven Segment Display.
Details for these and other modules can be found at www.digilentinc.com.
Demonstration design
The design pre-programmed onto the CPLD contains several functions that can be seen when the
provided peripheral modules are inserted into the appropriate ports.
Switches Æ port J8
PS/2 Æ port J7
7 Segment displays Æ ports J5/J6
Of course the design could be changed to use different ports, but these are the correct ones provided
in the sample design.
The CPLD implements both a counter as well as a PS/2 keyboard decoder. The display changes
between the two based on the value of SW4. SW1, 2 and 3 are not used in the design. BTN0 is the
system reset for the design. The ideal clock frequency for the design is 100 Hz, which is selected by
removing the jumper for J11.
When SW4 has the PS/2 decoder selected, the output on the display is the scan code for that letter.
Here are some scan codes, the rest can be found by searching the Internet.
Keyboard key Scan code Keyboard key Scan code
F1 05 F5 03
F2 06 F6 0B
F3 04 F7 83
F4 0C F8 0A
Design Recommendations
- The regulator provides V
CCIO
of 3.3V, so set the Default I/O Standard appropriately.
- Unused I/O should be set to Ground to minimize power
- Input Termination should be set to Keeper to minimize power consumption on any
potentially floating input pins.