Chapter 6: Ps/2 Mouse/Keyboard Port - Xilinx Spartan-3 User Manual

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PS/2 Mouse/Keyboard Port
The Spartan-3 Starter Kit board includes a PS/2 mouse/keyboard port and the standard 6-
pin mini-DIN connector, labeled J3 on the board and indicated as
Figure 6-1
Only pins 1 and 5 of the connector attach to the FPGA. A detailed schematic appears in
Figure
Table 6-1: PS/2 Connections to the Spartan-3 FPGA
Both a PC mouse and keyboard use the two-wire PS/2 serial bus to communicate with a
host device, the Spartan-3 FPGA in this case. The PS/2 bus includes both clock and data.
Both a mouse and keyboard drive the bus with identical signal timings and both use 11-bit
words that include a start, stop and odd parity bit. However, the data packets are
organized differently for a mouse and keyboard. Furthermore, the keyboard interface
allows bidirectional data transfers so the host device can illuminate state LEDs on the
keyboard.
The PS/2 bus timing appears
driven when data transfers occur, and otherwise they are held in the idle state at logic
High. The timings define signal requirements for mouse-to-host communications and
Spartan-3 Starter Kit Board User Guide
UG130 (v1.1) May 13, 2005
shows the PS/2 connector, and
A-7.
Figure 6-1: PS/2 DIN Connector
PS/2 DIN Pin
1 DATA (PS2D)
2 Reserved
3 GND
4 Voltage Supply
5 CLK (PS2C)
6 Reserved
Table 6-2
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Table 6-1 shows the signals on the connector.
1
2
4 3
6
5
UG130_c6_01_042404
Signal
and Figure 6-2. The clock and data signals are only
Chapter 6
in Figure 1-2.
9
FPGA Pin
M15
—
GND
—
M16
—
27