21. PS/2
21.1 Characteristics
The PS/2 pad IO’s characteristics are:
– support 5.5V (min: 4.5V, max: 5.5V)
– open drain type
– Output voltage level threshold, MCU driving low thru a 1kΩ pull-up: VOLmax = 0,7V
– fall time with 1kΩ pull-up and 500pF load: 250ns < Tfall < 1µs
– internal 2.2kΩ to 10kΩ pull-up at Vcc (5V), controlled by firmware.
– High impedance output when disabled.
Figure 21-1. USB pad and PS/2 pad multiplexing
PS/2 Pad
D+ / SCK
D- / SDATA
USB Pad
Bit
7
-
6
-
5
-
4
-
3
-
2
-
1
-
0
PS2EN
R/W
0
PS2CON
Read/Write
Initial Value
R
0
R
0
R
0
R
0
R
0
R
0
R
0
• Bit 7:1 – Reserved bits
Do not set these bits.
• Bit 0 – PS2EN : PS/2 Pad Enable
Set this bit to “1” to enable the PS/2 pad.
Set this bit to “0” to disable the PS/2 pad.
For more information about pad driving, see “USB/PS2 Software Output Enable register –
UPOE” on page 194.
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AT90USB82/162
7707D–AVR–07/08
ATMEL [ ATMEL ]
