Hardware Reference
In-Depth Information
Table
10-3
summarizes the GPIO Pads Control register. Note that to be successful
setting values in this register, the field labeled PASSWRD must receive the value 0x5A.
This is a simple measure to avoid having the values trashed by an accidental write to
this location.
Table 10-3.
GPIO Pads Control
Bits
Field
Description
I/O
Reset
31:24
PASSWRD
0x5A
Must be 0x5A when writing
W
0x00
23:05
Reserved
0x00
Write as zero, read as don't
care
R/W
04:04
SLEW
Slew rate
0
Slew rate limited
R/W
1
1
Slew rate not limited
03:03
HYST
Enable input hysterisis
0
Disabled
R/W
1
1
Enabled
02:00
DRIVE
Drive strength
R/W
3
0
2 mA
1
4 mA
2
6 mA
3
8 mA (default except 28 to 45)
4
10 mA
5
12 mA
6
14 mA
7
16 mA (GPIO 28 to 45)
Testing Pull-up State
If you want to test the state of the pull-up resistors, the following procedure can be used:
1.
Make sure no connection is attached so that the input can
float.
2.
Configure the GPIO pin as an input.
3.
Configure the GPIO as active high (that is, not
active low
).
