Chapter 3 — Theory of Operation
58 CV30 Fixed Mount Computer Service Manual
System Function
Battery Monitoring
During operation, the main processor periodically reads the battery voltage
and then estimates the amount of charge left in the battery pack. The
voltage level is reflected in the power bar settings in the operating system.
Whenever the battery voltage is read, the charger will be able to give an
accurate reading.
The BK_PWR comes directly from the main battery contacts. This signal is
presented to the A2D in the Audio CODEC IC. The processor periodically
reads this battery voltage only while the CODEC is ON, controlled by
signal AUDIO_CODEC_PWR_EN.
Microchip PIC Controller
The Microchip PIC controller has several housekeeping tasks in the CV30:
• External power source detect
• Cold / Warm RESET
• Status LED control
• Slave I2C communications
• Slave one wire communications
• ON/OFF key detection
• Sleep mode detect
• Battery temp monitoring and charger enable
• Detect headset connection
• EEPROM storage of unit configuration
External Power Source Detect
The PIC controller has a voltage detector connected to it that detects the
presence of the external power source. The voltage detector monitors the
SYS_PWR and has a threshold of 8 V. If the SYS_PWR voltage is above
this threshold, the system assumes that the external power source is
available. If the SYS_PWR voltage is below 8 V, the system determines that
the CV30 should go into critical suspend. The signal
nBATT_FAULT_DET from the voltage detector circuit routed to the PIC,
triggers the processor to “wake up” when an external power source is
detected.
Cold/Warm Reset and Clean Boot
The PIC controller also has the responsibility of providing the system with
a cold reset, warm reset, and a clean boot. The following block diagram
details the RESET path.
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