ATxmega32A4 Atmel Corporation, ATxmega32A4 Datasheet - Page 113

• Manufacturer Part Number: ATxmega32A4
• Manufacturer: Atmel Corporation

Specifications of ATxmega32A4

• Flash (kbytes): 32 Kbytes
• Pin Count: 44
• Max. Operating Frequency: 32 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 34
• Ext Interrupts: 34
• Usb Speed: No
• Usb Interface: No
• Spi: 7
• Twi (i2c): 2
• Uart: 5
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 12
• Adc Resolution (bits): 12
• Adc Speed (ksps): 2000
• Analog Comparators: 2
• Resistive Touch Screen: No
• Dac Channels: 2
• Dac Resolution (bits): 12
• Temp. Sensor: Yes
• Crypto Engine: AES/DES
• Sram (kbytes): 4
• Eeprom (bytes): 1024
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: Yes
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.6 to 3.6
• Operating Voltage (vcc): 1.6 to 3.6
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 5
• Output Compare Channels: 16
• Input Capture Channels: 16
• Pwm Channels: 16
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

10.3.2
10.4
10.5
10.5.1
10.5.2
Main Power Loss
Main Reset and Start-up Sequence
Battery Backup Brown-Out Detection
Battery Backup enabled
Battery Backup failed and not enabled
The the 32-kHz crystal oscillator, oscillator failure detection and Real Time Counter must be
enabled from software before they can be used.
The Battery Backup Brown-Out Detector (BBBOD) ensures detection of falling power in the Bat-
tery Backup Module before the oscillator stops. When the V
BBBOD threshold voltage, the BOD Flag (BBBODF) will be set.
The BBBOD is sampled from the 1 Hz output of an ultra low power oscillator, and only designed
for detecting slow changes in the V
The BBBOD is turned off when the device runs from the main power. It is enabled when the Bat-
tery Backup Module is switched to be powered from the V
When the main power drops below the programmed BOD threshold voltage, the device will:
1. Switch the Battery Backup Module to be powered from the V
2. Ignore any input signals to the Battery Backup Module.
3. The part of the device that is only powered from V
The Battery Backup System adds some considerations regarding main reset and start-up
sequence. At every start-up after main reset the software should:
1. Check for sufficient power on V
2. Check the Battery Backup Module status by reading the BBPODF and BBBODF flags.
3. Enable access to the Battery Backup Module, by setting the Access Enable (ACCEN) bit.
Based on the status in Battery Backup Module, two different things should be done after the ini-
tial sequence. Each is described in the two sections below.
If BBPODF and/or BBBODF is not set, it indicates that the Battery Backup Modules has not had
any power loss. Then the device should:
1. Set the Access Enable (ACCEN) bit
2. Check for 32-Khz Crystal Oscillator failure by reading the XOSC Failure flag.
If the XOSC Failure flag is cleared no further actions is required.
If the XOSC Failure flag is set, this indicates a failure on the external oscillator in the Battery
Backup Module. The software should assume that the RTC counter value is invalid and take
appropriate action.
If BBPODF and/or BBBODF is set this indicate that voltage on the V
sometime during the period when the rest of the device was unpowererd. The following proce-
dure should be followed:
enabled.
BAT
BAT
pin voltage level.
pin by reading the BBPWR flag.
CC
will be reset.
BAT
pin after a main power BOD.
BAT
BAT
pin voltage drops below the
pin. The BBBOD is
BAT
pin has had a drop