JN517X Datasheet, PDF (62/100 Pages) NXP Semiconductors – Supports multiple network stacks

NXP Semiconductors
JN517x
IEEE802.15.4 Wireless Microcontroller
10.3 Sleep mode
The JN517x enters sleep mode through software control. In this mode most of the internal
chip functions are shut down to save power, however the state of DIO pins are retained,
including the output values and pull-up enables, and this therefore preserves any interface
to the outside world.
When entering into sleep mode, there is an option to retain the RAM contents throughout
the sleep period. If the wake-up timers are not to be used for a wake-up event and the
application does not require them to run continually, then power can be saved by
switching off the 32 kHz oscillator if selected as the 32 kHz system clock through software
control. The oscillator is restarted when a wake-up event occurs.
Whilst in sleep mode, one of 4 possible events can cause a wake-up to occur: transitions
on DIO inputs, expiry of wake-up timers, pulse counters maturing or comparator events. If
any of these events occur, and the relevant interrupt is enabled, then an interrupt is
generated that will cause a wake-up from sleep. It is possible for multiple wake-up
sources to trigger an event at the same instant and only one of them will be accountable
for the wake-up period. It is therefore necessary in software to remove all other pending
wake-up events prior to requesting entry back into sleep mode; otherwise, the device will
reawaken immediately.
When wake-up occurs, a similar sequence of events to the reset process described in
Section 9.5.1 happens, including the checking of the supply voltage by the Supply Voltage
Monitor (Section 9.5.4). The high-speed RC oscillator is started up, once stable the power
to the CPU sub-system is enabled and the reset is removed. Software determines that this
is a reset from sleep and so commences with the wake-up process. If RAM contents were
held through sleep, wake-up is quicker as the software does not have to initialize RAM
contents meaning the application can recommence more quickly. See Section 14.3.5 for
wake-up timings.
10.3.1 Wake-up timer event
The JN517x contains two 41-bit wake-up timers that are counters clocked from the 32 kHz
oscillator, and can be programmed to generate a wake-up event. Following a wake-up
event, the timers continue to run. These timers are described in Section 9.10.3.
Timer events can be generated from both of the timers; one is intended for use by the
802.15.4 protocol, the other being available for use by the application running on the
CPU. These timers are available to run at any time, even during sleep mode.
10.3.2 DIO event
Any DIO pin when used as an input has the capability, by detecting a transition, to
generate a wake-up event. Once this feature has been enabled, the type of transition can
be specified (rising or falling edge). Even when groups of DIO lines are configured as
alternative functions such as the UARTs or Timers, any input line in the group can still be
used to provide a wake-up event. This means that an external device communicating over
the UART can wake up a sleeping device by asserting its RTS signal pin (which is the
CTS input of the JN517x).
JN517X
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2.0 — 8 November 2016
© NXP Semiconductors N.V. 2016. All rights reserved.
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