ATMEGA128A-AUR Atmel, ATMEGA128A-AUR Datasheet - Page 115

• Manufacturer Part Number: ATMEGA128A-AUR
• Description: MCU AVR 128K FLASH 16MHZ 64TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA128A-AUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: EBI/EMI, I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 128KB (64K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 4K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

15.3
8151H–AVR–02/11
Accessing 16-bit Registers
Interrupt flag and mask bits for output compare unit C are added.
The 16-bit Timer/Counter has improvements that will affect the compatibility in some special
cases.
The TCNTn, OCRnA/B/C, and ICRn are 16-bit registers that can be accessed by the AVR CPU
via the 8-bit data bus. The 16-bit register must be byte accessed using two read or write opera-
tions. Each 16-bit timer has a single 8-bit register for temporary storing of the high byte of the 16-
bit access. The same Temporary Register is shared between all 16-bit registers within each 16-
bit timer. Accessing the low byte triggers the 16-bit read or write operation. When the low byte of
a 16-bit register is written by the CPU, the high byte stored in the Temporary Register, and the
low byte written are both copied into the 16-bit register in the same clock cycle. When the low
byte of a 16-bit register is read by the CPU, the high byte of the 16-bit register is copied into the
Temporary Register in the same clock cycle as the low byte is read.
Not all 16-bit accesses uses the Temporary Register for the high byte. Reading the OCRnA/B/C
16-bit registers does not involve using the Temporary Register.
To do a 16-bit write, the high byte must be written before the low byte. For a 16-bit read, the low
byte must be read before the high byte.
The following code examples show how to access the 16-bit timer registers assuming that no
interrupts updates the temporary register. The same principle can be used directly for accessing
the OCRnA/B/C and ICRn Registers. Note that when using “C”, the compiler handles the 16-bit
access.
• FOCnA, FOCnB, and FOCnC are added in the new TCCRnC Register.
• WGMn3 is added to TCCRnB.
ATmega128A
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