Atmel ATSAM3U-EK Data Sheet
Evaluation Kit Hardware
SAM3U-EK Evaluation Kit User Guide
4-5
6478E–ATARM–30-Mar-11
Figure 4-4.
External Clock Source
4.3.4
Reset and Wake-Up Circuitry
The on-board NRST button BP1 and NRSTB button BP2 provide the SAM3U4E with external reset con-
trol. The on-board WAKE-UP button BP3 can be used to wake up the chip from low power modes.
trol. The on-board WAKE-UP button BP3 can be used to wake up the chip from low power modes.
Figure 4-5.
System Buttons
The NRST pin is bidirectional. It is handled by the on-chip reset controller. It can be driven low to provide
a reset signal out to the external components. Conversely, it can be asserted low from the outside to
reset the microcontroller, its core and peripherals, Backup region (RTC, RTT and Supply Controller)
excepted. The NRST pin integrates a permanent pull-up resistor of about 100 kOhm to VDDIO.
a reset signal out to the external components. Conversely, it can be asserted low from the outside to
reset the microcontroller, its core and peripherals, Backup region (RTC, RTT and Supply Controller)
excepted. The NRST pin integrates a permanent pull-up resistor of about 100 kOhm to VDDIO.
On the SAM3U-EK board, the NRST signal is connected to the LCD module and JTAG port.
The NRSTB pin is an input-only signal that enables the asynchronous reset of the SAM3U4E series
when asserted low. The NRSTB pin integrates a permanent pull-up resistor of about 15 kOhm. This
allows the connection of a simple push button for implementing a system-user reset. Whatever the
mode, this pin will reset the chip including the Backup region (RTC, RTT and Supply Controller). It
makes the chip behave as for a Power-on reset. An external capacitor (10 nF) is connected between
NRSTB and VDDIO to enforce the signal stability on this pin.
when asserted low. The NRSTB pin integrates a permanent pull-up resistor of about 15 kOhm. This
allows the connection of a simple push button for implementing a system-user reset. Whatever the
mode, this pin will reset the chip including the Backup region (RTC, RTT and Supply Controller). It
makes the chip behave as for a Power-on reset. An external capacitor (10 nF) is connected between
NRSTB and VDDIO to enforce the signal stability on this pin.
XIN32
XIN1
XOUT 32
XOUT 1
XOUT 1
XIN1
XOUT 32
XIN32
DG ND
DG ND
DG ND
DG ND
XIN
XOUT
XOUT
XIN32
XOUT 32
XOUT 32
C 26
20pF
20pF
C 26
20pF
20pF
R 7
0R
R 7
0R
Y 1
12.000MHz
Y 1
12.000MHz
C 25
20pF
20pF
C 25
20pF
20pF
MN1B
S AM3U
S AM3U
MN1B
S AM3U
S AM3U
XIN32
144
XOUT 32
143
XIN
36
XOUT
35
G ND1
18
G NDP LL
33
G NDUT MI
43
G ND2
52
G ND3
60
G NDANA
75
G ND4
90
G ND5
126
G NDB U
140
C 27
20pF
20pF
C 27
20pF
20pF
R 6
0R
R 6
0R
Y 2
32.768K Hz
Y 2
32.768K Hz
1
2
3
C 24
20pF
20pF
C 24
20pF
20pF
J 1
J 1
1
2
3
5
5
4
R 8
DNP
R 8
DNP
DG ND
V B U
NR S T
NR S T B
F W UP
WAKE _ UP#
B P 2
B P 2
1
4
2
3
B P 1
B P 1
1
4
2
3
B P 3
B P 3
1
4
2
3
R 65
100K
100K
R 65
100K
100K