ATMEGA645V-8AU Atmel, ATMEGA645V-8AU Datasheet - Page 33
![IC AVR MCU FLASH 64K 64TQFP](/photos/12/13/121332/313-64-tqfp_sml.jpg)
ATMEGA645V-8AU
Manufacturer Part Number
ATMEGA645V-8AU
Description
IC AVR MCU FLASH 64K 64TQFP
Manufacturer
Atmel
Series
AVR® ATmegar
Datasheet
1.ATMEGA325-16MU.pdf
(362 pages)
Specifications of ATMEGA645V-8AU
Core Processor
AVR
Core Size
8-Bit
Speed
8MHz
Connectivity
SPI, UART/USART, USI
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
53
Program Memory Size
64KB (32K x 16)
Program Memory Type
FLASH
Eeprom Size
2K x 8
Ram Size
4K 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
64-TQFP, 64-VQFP
Processor Series
ATMEGA64x
Core
AVR8
Data Bus Width
8 bit
Data Ram Size
4 KB
Interface Type
SPI, UART, USI
Maximum Clock Frequency
8 MHz
Number Of Programmable I/os
54
Number Of Timers
3
Operating Supply Voltage
1.8 V to 5.5 V
Maximum Operating Temperature
+ 85 C
Mounting Style
SMD/SMT
Minimum Operating Temperature
- 40 C
On-chip Adc
10 bit, 8 Channel
Controller Family/series
AVR MEGA
No. Of I/o's
54
Eeprom Memory Size
2KB
Ram Memory Size
4KB
Cpu Speed
8MHz
No. Of Timers
3
Rohs Compliant
Yes
Data Rom Size
2 KB
Height
1 mm
Length
14 mm
Supply Voltage (max)
5.5 V
Supply Voltage (min)
2.7 V
Width
14 mm
For Use With
ATSTK600-TQFP64 - STK600 SOCKET/ADAPTER 64-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 SYSTEM
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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- Download datasheet (7Mb)
8.10.2
2570M–AVR–04/11
CLKPR – Clock Prescale Register
The CAL6..0 bits are used to tune the frequency within the selected range. A setting of 0x00
gives the lowest frequency in that range, and a setting of 0x7F gives the highest frequency in the
range.
• 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 zero. CLKPCE is
cleared by hardware four cycles after it is written or when CLKPS bits are written. Rewriting the
CLKPCE bit within this time-out period does neither extend the time-out period, nor clear the
CLKPCE bit.
• Bits 3:0 – CLKPS3:0: Clock Prescaler Select Bits 3 - 0
These bits define the division factor between the selected clock source and the internal system
clock. These bits can be written run-time to vary the clock frequency to suit the application
requirements. As the divider divides the master clock input to the MCU, the speed of all synchro-
nous peripherals is reduced when a division factor is used. The division factors are given in
Table 8-11 on page
To avoid unintentional changes of clock frequency, a special write procedure must be followed
to change the CLKPS bits:
1. Write the Clock Prescaler Change Enable (CLKPCE) bit to one and all other bits in
2. Within four cycles, write the desired value to CLKPS while writing a zero to CLKPCE.
Interrupts must be disabled when changing prescaler setting to make sure the write procedure is
not interrupted.
The CKDIV8 Fuse determines the initial value of the CLKPS bits. If CKDIV8 is unprogrammed,
the CLKPS bits will be reset to “0000”. If CKDIV8 is programmed, CLKPS bits are reset to
“0011”, giving a division factor of 8 at start up. This feature should be used if the selected clock
source has a higher frequency than the maximum frequency of the device at the present operat-
ing conditions. Note that any value can be written to the CLKPS bits regardless of the CKDIV8
Fuse setting. The Application software must ensure that a sufficient division factor is chosen if
the selected clock source has a higher frequency than the maximum frequency of the device at
the present operating conditions. The device is shipped with the CKDIV8 Fuse programmed.
Table 8-11.
Bit
(0x61)
Read/Write
Initial Value
CLKPS3
CLKPR to zero.
0
0
0
0
0
CLKPCE
Clock Prescaler Select
R/W
7
0
CLKPS2
33.
0
0
0
0
1
R
6
–
0
CLKPS1
5
R
–
0
0
0
1
1
0
R
4
–
0
ATmega325/3250/645/6450
CLKPS0
CLKPS3
R/W
3
0
1
0
1
0
CLKPS2
See Bit Description
R/W
2
Clock Division Factor
CLKPS1
R/W
1
16
CLKPS0
1
2
4
8
R/W
0
CLKPR
33
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