Digilent DIO1 - Manual (Page 4)

Digilent DIO1 Reference Manual Digilent, Inc.
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Switches
The eight slide switches can be used to connect
either Vdd or GND to eight pins on interface
connecter B. The switches exhibit about 2ms of
bounce, and no active debouncing circuit is
employed. A 4.7K-ohm series resistor is used
for nominal input protection.
PS2 port
The DIO1 board includes a 6-pin
mini-DIN connector that can
accommodate a PS2 mouse or PS2
keyboard connection. Both the
mouse and keyboard use a two-
wire serial bus (including clock
and data) to communicate with a
host device, and both drive the bus
with identical signal timings. Both
use 11-bit words that include a start, stop and
odd parity bit, but the data packets are
organized differently, and the keyboard
interface allows bi-directional data transfers (so
the host device can illuminate state LEDs on
the keyboard).
Bus timings are shown below. The clock and
data signals are only driven when data transfers
occur, and otherwise they are held in the “idle”
state at logic ‘1’. The timings define signal
requirements for mouse-to-host
communications and bi-directional keyboard
communications.
PS2 Connector front view
Pin 1
Pin 5 Pin 6
Bottom-up
hole pattern
PS2 Pin Definitions
Pin Function
1 Data
2 Reserved
3 GND
4 Vdd
5 Clock
6 Reserved
1
5
3
2
4
6
GND
Vdd
To
Connector
RP6 & 7
4.7 KOhm
T
CK
T
SU
Edge 0
Edge 10
CLK
DATA
T
CK
T
SU
Clock time
Data-to-clock setup time
30us
5us
50us
25us
Symbol Parameter Min Max
T
HLD
Clock-to-data hold time 5us 25us
T
HLD
T
CK
'1' stop bit '0' start bit