© NXP Laboratories UK 2012
JN-DS-JN5142 1v0
23
RESETN
C1
R1
JN5142
VDD
18k
470nF
Figure 12: External Reset Generation
The external resistor and capacitor provide a simple reset operation when connected to the RESETN pin.
6.2 External Reset
An external reset is generated by a low level on the RESETN pin. Reset pulses longer than the minimum pulse width
will generate a reset during active or sleep modes. Shorter pulses are not guaranteed to generate a reset. The
JN5142 is held in reset while the RESETN pin is low. When the applied signal reaches the Reset Threshold Voltage
(V
RST
) on its positive edge, the internal reset process starts.
The JN5142 has an internal 300k
Ω pull-up resistor connect to the RESETN pin. The pin is an input for an external
reset only.
Internal Reset
RESETN pin
Reset
Figure 13: External Reset
6.3 Software Reset
A system reset can be triggered at any time through software control, causing a full chip reset and invalidating the
RAM contents. For example this can be executed within a user‟s application upon detection of a system failure.
6.4 Supply Voltage Monitor (SVM)
An internal Supply Voltage Monitor (SVM) is used to monitor the supply voltage to the JN5142; this can be used
whilst the device is awake or is in CPU doze mode. Dips in the supply voltage below a variable threshold can be
detected and can be used to cause the JN5142 to perform a chip reset. Equally, dips in the supply voltage can be
detected and used to cause an interrupt to the processor, when the voltage either drops below the threshold or rises
above it.
The supply voltage detect is enabled by default from power-up and can extend the reset during power-up. This will
keep the CPU in reset until the voltage exceeds the SVM threshold voltage. The threshold voltage is configurable to
1.95V, 2.0V, 2.1V, 2.2V, 2.3V, 2.4V, 2.7V and 3.0V and is controllable by software. From power-up the threshold is