ATMEGA16A-PU Atmel, ATMEGA16A-PU Datasheet - Page 128
Manufacturer Part Number
MCU AVR 16K FLASH 16MHZ 40-PDIP
Specifications of ATMEGA16A-PU
I²C, SPI, UART/USART
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
Program Memory Size
16KB (8K x 16)
Program Memory Type
512 x 8
1K x 8
Voltage - Supply (vcc/vdd)
2.7 V ~ 5.5 V
-40°C ~ 85°C
Package / Case
40-DIP (0.600", 15.24mm)
Data Bus Width
Data Ram Size
Maximum Clock Frequency
Number Of Programmable I/os
Number Of Timers
Maximum Operating Temperature
+ 85 C
3rd Party Development Tools
Development Tools By Supplier
ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT
Minimum Operating Temperature
- 40 C
8-ch x 10-bit
Operating Supply Voltage
No. Of I/o's
Eeprom Memory Size
Ram Memory Size
For Use With
ATSTK600 - DEV KIT FOR AVR/AVR32ATSTK500 - PROGRAMMER AVR STARTER KIT
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Asynchronous Operation of the Timer/Counter2
Figure 17-11. Timer/Counter Timing Diagram, Clear Timer on Compare Match Mode, with Pres-
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 OCIE2 and TOIE2.
2. Select clock source by setting AS2 as appropriate.
3. Write new values to TCNT2, OCR2, and TCCR2.
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 Oscillator is optimized for use with a 32.768 kHz watch crystal. Applying an external
• When writing to one of the registers TCNT2, OCR2, or TCCR2, the value is transferred to a
• When entering Power-save or Extended Standby mode after having written to TCNT2,
Timer/Counter2, the Timer Registers TCNT2, OCR2, and TCCR2 might be corrupted. A safe
procedure for switching clock source is:
clock to the TOSC1 pin may result in incorrect Timer/Counter2 operation. The CPU main
clock frequency must be more than four times the Oscillator frequency.
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 for example that writing to TCNT2 does not disturb an OCR2 write in progress.
To detect that a transfer to the destination register has taken place, the Asynchronous Status
Register – ASSR has been implemented.
OCR2, or TCCR2, 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 OCR2 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.
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