SL876Q5-A
Product User Guide
1VV0301333 Rev. 2
Page 38 of 68
2017-06-27
Control Input Signals
ON-OFF (input) and SYSTEM-ON (output)
The SL876Q5-A module has three power states: OFF, RESET, and ON.
The OFF state is when power is removed from the module.
Upon initial application of power, the module enters the RESET state until the internal reset
process is completed. It then transitions to the ON state.
In the ON state, the module will transition to either the RUN or HIBERNATE substate
depending on the ON-OFF pin status.
If the ON-OFF pin is high, the module will transition to the RUN substate.
If the ON-OFF pin is low, the module will transition to the HIBERNATE substate.
The ON state is indicated by a logic high output on the SYSTEM-ON signal.
Note
: The ON_OFF pin must not be tied to V18 because it must be brought low, then high to
transition out of a commanded hibernate state.
The module will transition to the RESET state when external reset (nRESET) is pulled low, or
upon internal reset (e.g. supply voltage out of spec). The external nRESET signal takes
precedence over the state of the ON-OFF signal. SYSTEM-ON will be logic low.
While in the ON state, there are three substates, depending upon commands or selected power
management modes. The three substates are: HIBERNATE, STANDBY, and RUN.
The module transitions between RUN and STANDBY via TricklePower modes; and between
RUN and HIBERNATE via PushToFixII and SiRFaware modes. It can also transition from RUN
to HIBERNATE by de-asserting the ON-OFF signal. The firmware is configured to transition
from HIBERNATE to RUN when data is received on the RX pin.
In HIBERNATE and STANDBY, the SYSTEM-ON signal will be logic low; in RUN, it will be
logic high.
To execute an orderly shutdown, place the module in the HIBERNATE substate, then remove
power.
Also, see
Section 8.5.2 nReset.
nReset
The module will generate an internal reset as appropriate. Therefore, no external signal is
required for the module to operate properly and this pin may be left unconnected. However, it
is desirable to bring it out to a test point if otherwise unconnected.
If an external reset is desired, the signal must be either open collector or open drain without
any form of pull up. Do not pull this line high with either a pull up or a driven logic one. When
this line is pulled low, the module will immediately transition into reset mode.
When the external reset is released, the module will go through its normal power up sequence
provided the V18 supply is within specifications. See
Section 8.5.1 ON-OFF (input) and
Pulling nRESET low at any time forces the module into the reset state irrespective of the ON-
OFF signal. In the reset state, the SYSTEM-ON signal is low.
Once the nRESET signal is released the module will transition to the HIBERNATE state or to
the ON state as determined by the ON-OFF signal input.
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