ATMEGA3250PV-10AU Atmel, ATMEGA3250PV-10AU Datasheet - Page 147

• Manufacturer Part Number: ATMEGA3250PV-10AU
• Description: IC MCU AVR 32K FLASH 100-TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA3250PV-10AU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 10MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 69
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 2K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 100-TQFP, 100-VQFP
• Processor Series: ATMEGA32x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 2 KB
• Interface Type: SPI, UART, USI
• Maximum Clock Frequency: 10 MHz
• Number Of Programmable I/os: 69
• Number Of Timers: 3
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 10 bit, 8 Channel
• Data Rom Size: 1 KB
• Operating Supply Voltage: 1.8 V to 5.5 V
• Operating Temperature Range: - 40 C to + 85 C
• A/d Bit Size: 10 bit
• A/d Channels Available: 8
• Height: 1 mm
• Length: 14 mm
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 1.8 V
• Width: 14 mm
• For Use With: ATSTK600-TQFP100 - STK600 SOCKET/ADAPTER 100-TQFP770-1007 - ISP 4PORT ATMEL AVR MCU SPI/JTAG770-1005 - ISP 4PORT FOR ATMEL AVR MCU JTAG770-1004 - ISP 4PORT FOR ATMEL AVR MCU SPIATAVRISP2 - PROGRAMMER AVR IN SYSTEMATSTK504 - STARTER KIT AVR EXP MOD 100P LCD
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ATMEGA3250PV-8AU; ATMEGA3250PV-8AU

16.9
8023F–AVR–07/09
Asynchronous Operation of Timer/Counter2
When Timer/Counter2 operates asynchronously, some considerations must be taken.
• Warning: When switching between asynchronous and synchronous clocking of
1. Disable the Timer/Counter2 interrupts by clearing OCIE2A and TOIE2.
2. Select clock source by setting AS2 as appropriate.
3. Write new values to TCNT2, OCR2A, and TCCR2A.
4. To switch to asynchronous operation: Wait for TCN2UB, OCR2UB, and TCR2UB.
5. Clear the Timer/Counter2 Interrupt Flags.
6. Enable interrupts, if needed.
• The CPU main clock frequency must be more than four times the Oscillator frequency.
• When writing to one of the registers TCNT2, OCR2A, or TCCR2A, the value is transferred to a
• When entering Power-save or ADC Noise Reduction mode after having written to TCNT2,
• If Timer/Counter2 is used to wake the device up from Power-save or ADC Noise Reduction
1. Write a value to TCCR2A, TCNT2, or OCR2A.
2. Wait until the corresponding Update Busy Flag in ASSR returns to zero.
3. Enter Power-save or ADC Noise Reduction mode.
• When the asynchronous operation is selected, the 32.768 kHz Oscillator for Timer/Counter2 is
Timer/Counter2, the Timer Registers TCNT2, OCR2A, and TCCR2A might be corrupted. A
safe procedure for switching clock source is:
temporary register, and latched after two positive edges on TOSC1. The user should not write
a new value before the contents of the temporary register have been transferred to its
destination. Each of the three mentioned registers have their individual temporary register,
which means that e.g. writing to TCNT2 does not disturb an OCR2A write in progress. To
detect that a transfer to the destination register has taken place, the Asynchronous Status
Register – ASSR has been implemented.
OCR2A, or TCCR2A, the user must wait until the written register has been updated if
Timer/Counter2 is used to wake up the device. Otherwise, the MCU will enter sleep mode
before the changes are effective. This is particularly important if the Output Compare2 interrupt
is used to wake up the device, since the Output Compare function is disabled during writing to
OCR2A or TCNT2. If the write cycle is not finished, and the MCU enters sleep mode before the
OCR2UB bit returns to zero, the device will never receive a compare match interrupt, and the
MCU will not wake up.
mode, precautions must be taken if the user wants to re-enter one of these modes: The
interrupt logic needs one TOSC1 cycle to be reset. If the time between wake-up and reentering
sleep mode is less than one TOSC1 cycle, correct interrupt handling is not guaranteed. If the
user is in doubt whether the time before re-entering Power-save or ADC Noise Reduction
mode is sufficient, the following algorithm can be used to ensure that one TOSC1 cycle has
elapsed:
always running, except in Power-down and Standby modes. After a Power-up Reset or wake-
up from Power-down or Standby mode, the user should be aware of the fact that this Oscillator
might take as long as one second to stabilize. The user is advised to wait for at least one
second before using Timer/Counter2 after power-up or wake-up from Power-down or Standby
mode. The contents of all Timer/Counter2 Registers must be considered lost after a wake-up
from Power-down or Standby mode due to unstable clock signal upon start-up, no matter
whether the Oscillator is in use or a clock signal is applied to the TOSC1 pin.
ATmega325P/3250P
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