
REF: BB_SRM_xM BeagleBoard-xM System
Reference Manual
Revision A2
Page 62 of 164
8.9.4 Reset Signals
The BeagleBoard uses three distinct reset circuits:
o Warm Reset
o Cold Reset
o User Reset
Figure 28 shows the connections for the Reset interfaces.
Figure 28. Reset Circuitry
8.9.4.1 Warm Reset
The warm reset is generated by the processor on power up. The nRESWARM signal is a
bidirectional reset. When an internal reset occurs, nRESWARM goes low and resets all
the peripherals and the TPS65950. The TPS65950 can be configured to perform a warm
reset of the device to bring it into a known defined state by detecting a request for a warm
reset on the NRESWARM pin. The minimum duration of the pulse on the nRESWARM
pin should be two 32-kHz clock cycles. The nRESWARM output is open-drain;
consequently, an external pullup resistor is required. There is no way for the user to
generate a warm reset on the BeagleBoard.
8.9.4.2 Cold Reset
On power up as shown in Figure 27, the TPS65950 generates nRESPWRON, power on
reset. The signal from the TPS65950 is an output only and is not an open drain signal.
By running the signal through a buffer, SN74LVC2G07, the signal becomes open drain,
which requires a pullup on the signal. This will allow the nRESPWRON signal to be
P9
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26
28
1
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27
R61
4.7K
VIO_1V8
U5A
SN74LVC2G07DCKR
1
2
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BAT
IO_1P8
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S
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B13
A13
A11
nRESWARM
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R42
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C12
0.1uF
VBAT
PWRON
R59 4.7K
S2
B3F-1000
1 3
2 4
R53
DNI
nRESWARM
VIO_1V8
PROCESSOR
U4B AM3730
AH25
AF24
SYS_nRESPWRON
SYS_nRESWARM/GPIO_30
nRESET
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