PS/2
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 88. 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 |
PS2CON |
|
|
|
|
|
|
|
|
|
|
Read/Write |
R |
R |
R |
R |
R |
R |
R |
R/W |
|
Initial Value |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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 190.
The UPOE register described in this section allows to read or writes values on the pad. PS/2 protocol must be entirely handled by software.
213
7707A–AVR–01/07
