ATMEGA165-16AI Atmel, ATMEGA165-16AI Datasheet - Page 29

• Manufacturer Part Number: ATMEGA165-16AI
• Description: IC AVR MCU 16K 16MHZ 64TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA165-16AI

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 54
• Program Memory Size: 16KB (8K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 1K 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: 64-TQFP, 64-VQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Clock Output Buffer
Timer/Counter Oscillator
System Clock Prescaler
Clock Prescale Register –
CLKPR
2573G–AVR–07/09
Table 12. Start-up Times for the External Clock Selection
When applying an external clock, it is required to avoid sudden changes in the applied
clock frequency to ensure stable operation of the MCU. A variation in frequency of more
than 2% from one clock cycle to the next can lead to unpredictable behavior. It is
required to ensure that the MCU is kept in Reset during such changes in the clock
frequency.
Note that the System Clock Prescaler can be used to implement run-time changes of
the internal clock frequency while still ensuring stable operation. Refer to “System Clock
Prescaler” on page 29 for details.
When the CKOUT Fuse is programmed, the system Clock will be output on CLKO. This
mode is suitable when chip clock is used to drive other circuits on the system. The clock
will be output also during reset and the normal operation of I/O pin will be overridden
when the fuse is programmed. Any clock source, including internal RC Oscillator, can be
selected when CLKO serves as clock output. If the System Clock Prescaler is used, it is
the divided system clock that is output when the CKOUT Fuse is programmed.
ATmega169 share the Timer/Counter Oscillator Pins (TOSC1 and TOSC2) with XTAL1
and XTAL2. This means that the Timer/Counter Oscillator can only be used when the
calibrated internal RC Oscillator is selected as system clock source. The Oscillator is
optimized for use with a 32.768 kHz watch crystal. See Figure 12 on page 25 for crystal
connection.
Applying an external clock source to TOSC1 can be done if EXTCLK in the ASSR Reg-
ister is written to logic one. See “Asynchronous operation of the Timer/Counter” on page
134 for further description on selecting external clock as input instead of a 32 kHz
crystal.
The ATmega165 system clock can be divided by setting the Clock Prescale Register –
CLKPR. This feature can be used to decrease power consumption when the require-
ment for processing power is low. This can be used with all clock source options, and it
will affect the clock frequency of the CPU and all synchronous peripherals. clk
clk
• Bit 7 – CLKPCE: Clock Prescaler Change Enable
The CLKPCE bit must be written to logic one to enable change of the CLKPS bits. The
CLKPCE bit is only updated when the other bits in CLKPR are simultaneously written to
Bit
Read/Write
Initial Value
SUT1..0
CPU
00
01
10
11
, and clk
Start-up Time from Power-
CLKPCE
down and Power-save
FLASH
R/W
7
0
are divided by a factor as shown in Table 13.
6 CK
6 CK
6 CK
R
6
–
0
R
5
–
0
R
4
0
–
Additional Delay from
Reset (V
Reserved
14CK + 4.1 ms
14CK + 65 ms
CLKPS3
R/W
14CK
3
CC
= 5.0V)
CLKPS2
See Bit Description
R/W
2
ATmega165/V
CLKPS1
R/W
Recommended Usage
BOD enabled
Fast rising power
Slowly rising power
1
CLKPS0
R/W
0
I/O
, clk
CLKPR
ADC
29
,