ATmega168A Atmel Corporation, ATmega168A Datasheet - Page 21

• Manufacturer Part Number: ATmega168A
• Manufacturer: Atmel Corporation

Specifications of ATmega168A

• Flash (kbytes): 16 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 23
• Ext Interrupts: 24
• Usb Speed: No
• Usb Interface: No
• Spi: 2
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 1
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 6
• Input Capture Channels: 1
• Pwm Channels: 6
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

8.4.2
8.5
8271D–AVR–05/11
I/O Memory
Preventing EEPROM Corruption
During periods of low V
too low for the CPU and the EEPROM to operate properly. These issues are the same as for
board level systems using EEPROM, and the same design solutions should be applied.
An EEPROM data corruption can be caused by two situations when the voltage is too low. First,
a regular write sequence to the EEPROM requires a minimum voltage to operate correctly. Sec-
ondly, the CPU itself can execute instructions incorrectly, if the supply voltage is too low.
EEPROM data corruption can easily be avoided by following this design recommendation:
Keep the AVR RESET active (low) during periods of insufficient power supply voltage. This can
be done by enabling the internal Brown-out Detector (BOD). If the detection level of the internal
BOD does not match the needed detection level, an external low V
be used. If a reset occurs while a write operation is in progress, the write operation will be com-
pleted provided that the power supply voltage is sufficient.
The I/O space definition of the ATmega48A/PA/88A/PA/168A/PA/328/P is shown in
Summary” on page
All ATmega48A/PA/88A/PA/168A/PA/328/P I/Os and peripherals are placed in the I/O space. All
I/O locations may be accessed by the LD/LDS/LDD and ST/STS/STD instructions, transferring
data between the 32 general purpose working registers and the I/O space. I/O Registers within
the address range 0x00 - 0x1F are directly bit-accessible using the SBI and CBI instructions. In
these registers, the value of single bits can be checked by using the SBIS and SBIC instructions.
Refer to the instruction set section for more details. When using the I/O specific commands IN
and OUT, the I/O addresses 0x00 - 0x3F must be used. When addressing I/O Registers as data
space using LD and ST instructions, 0x20 must be added to these addresses. The
ATmega48A/PA/88A/PA/168A/PA/328/P is a complex microcontroller with more peripheral units
than can be supported within the 64 location reserved in Opcode for the IN and OUT instruc-
tions. For the Extended I/O space from 0x60 - 0xFF in SRAM, only the ST/STS/STD and
LD/LDS/LDD instructions can be used.
For compatibility with future devices, reserved bits should be written to zero if accessed.
Reserved I/O memory addresses should never be written.
Some of the Status Flags are cleared by writing a logical one to them. Note that, unlike most
other AVRs, the CBI and SBI instructions will only operate on the specified bit, and can therefore
be used on registers containing such Status Flags. The CBI and SBI instructions work with reg-
isters 0x00 to 0x1F only.
The I/O and peripherals control registers are explained in later sections.
533.
ATmega48A/PA/88A/PA/168A/PA/328/P
CC,
the EEPROM data can be corrupted because the supply voltage is
CC
reset Protection circuit can
”Register
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