User Guide

PAMS
Technical Documentation
NME–3
Technical Information
Page 33
Issue 1 10/99
Description of gm8b Powerup/Powerdown behaviour
In a carphone there are 2 sources that wakeup the system in a normal
situation:
1. Ignition is turned on
2. The User presses the Powerbutton
In both situations the phone has to stay in Power On status as long as the
Userpresses the Powerbutton again or Ignition is turned OFF. It should not
be switched off when the software crashed
To gauranty this behaviour, we have added several extra circuits around
CCONT. In gm8b are 4 events that generate a 100mS pulse on poweronx
and switch on CCONT.:
1. Ignition is switched ON
2. Powerbutton is pressed
3. The Carbatteryvoltage comes up from below 3.8V (Brownout).
4. PURX goes down caused by a software crash
In order to decide if the PURX is going low because of a Softwarecrash, or
because of a regular Shutdown, there is a Powerdown signal going from
MAD to the Powercontrol unit. When the SW is initiating a Shutdown,
Powerdown is set high, and the Pulse generator is disabled, and no Pulse
is generated on the falling edge of PURX. The following pictures are
ilustrating the Powerup/Down behaviour.
Figure 10. regular Startup
Wakeupevent
(IGNS/Powerbutton)
PowerOnX
200us
200mS
PURX
50mS
Powerdown