Motorola W24 用户手册

The W24 power on consists of two primary phases:

Initial power up is hardware controlled by the Power-up/down circuit which monitors two 
power-up control signals: ON_N and IGN. If any of these two signals is asserted, the 
Power-up/down circuit will enable Voltage regulators and the power management IC. They will 
provide valid supply voltages to the processor which will start to boot.

The second phase is SW controlled. Processor checks the state of ON_N and IGN signals and if 
any of them is asserted, the CPU takes control over the voltage regulators and power management 
IC and holds them enabled.

Power down is controlled by SW - Once valid power-down condition occurs, CPU will release 
the signal which keeps the regulators and power management enabled, thus causing the W24 to 
power down. If this happened while IGN signal is still asserted, the regulators will remain active, 
and the unit will enter "Off mode".

W24 state is indicated at the interface connector by the hardware output signals RESET_N. The 
RESET_N signal indicates whether W24 is powered on or off. When the RESET_N is low, W24 
is powered-off. When it is high, W24 is powered-on.

As the power down process in W24 is SW controlled, if an unexpected reset occurs, the 
module will power down if it is not being held by the IGN signal. Therefore, although 
both ways of powering up/down are provided to user, we recommend using IGN as a sole 
power up/down control signal. By using IGN as a control signal, user insures that in case 
of an unexpected reset, the unit automatically turns on. If the IGN was not asserted, the 
unit will remain "OFF" after a reset.

Do not operate the W24 out of its electrical or environmental limits. Refer to the 
specifications chapter for details of these limits.

When the W24 power supply is stable above the minimum operating level and W24 is powered 
off, all of its circuits are disabled.

When W24 is turned on, by any of the methods described below, it will first perform an automatic 
initialization. When the initialization has completed, W24 resumes normal operation (stand alone 
mode), or turns on the G24 module (stacked modules) and resumes normal operation.

During the internal system-test process W24 may toggle several interface signals, which are 
visible to the application. These signals do not represent any valid state or data, and should be 
ignored by the customer application until the system-test has completed.

Valid Turn-on reasons are:

ON_N asserted low for 0.5s

IGNITION asserted

During FW upgrades (reflashing) make sure to power-up the W24 by IGN.