ATMEGA1281-16MU Atmel, ATMEGA1281-16MU Datasheet - Page 50
ATMEGA1281-16MU
Manufacturer Part Number
ATMEGA1281-16MU
Description
IC MCU AVR 128K FLASH 64-QFN
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA1281-16MU
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
54
Program Memory Size
128KB (64K x 16)
Program Memory Type
FLASH
Eeprom Size
4K x 8
Ram Size
8K 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-MLF®, 64-QFN
Processor Series
ATMEGA128x
Core
AVR8
Data Bus Width
8 bit
Data Ram Size
8 KB
Interface Type
2-Wire, SPI, UART
Maximum Clock Frequency
16 MHz
Number Of Programmable I/os
54
Number Of Timers
6
Operating Supply Voltage
4.5 V to 5.5 V
Maximum Operating Temperature
+ 85 C
Mounting Style
SMD/SMT
3rd Party Development Tools
EWAVR, EWAVR-BL
Development Tools By Supplier
ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT, ATAVRRZ541, ATAVRRAVEN, ATAVRRZRAVEN, ATAVRRZUSBSTICK, ATAVRISP2, ATAVRRZ201
Minimum Operating Temperature
- 40 C
On-chip Adc
10 bit, 8 channel
For Use With
ATSTK600-TQFP64 - STK600 SOCKET/ADAPTER 64-TQFPATAVRDB101 - MODULE DISPLAY LCD/RGB BACKLIGHT770-1007 - ISP 4PORT ATMEL AVR MCU SPI/JTAGATAVRISP2 - PROGRAMMER AVR IN SYSTEMATJTAGICE2 - AVR ON-CHIP D-BUG SYSTEM
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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9.13
9.13.1
9.13.2
2549M–AVR–09/10
Register Description
OSCCAL – Oscillator Calibration Register
CLKPR – Clock Prescale Register
• Bits 7:0 – CAL7:0: Oscillator Calibration Value
The Oscillator Calibration Register is used to trim the Calibrated Internal RC Oscillator to
remove process variations from the oscillator frequency. A pre-programmed calibration value is
automatically written to this register during chip reset, giving the Factory calibrated frequency as
specified in
the oscillator frequency. The oscillator can be calibrated to frequencies as specified in
1 on page
Note that this oscillator is used to time EEPROM and Flash write accesses, and these write
times will be affected accordingly. If the EEPROM or Flash are written, do not calibrate to more
than 8.8 MHz. Otherwise, the EEPROM or Flash write may fail.
The CAL7 bit determines the range of operation for the oscillator. Setting this bit to 0 gives the
lowest frequency range, setting this bit to 1 gives the highest frequency range. The two fre-
quency ranges are overlapping, in other words a setting of OSCCAL = 0x7F gives a higher
frequency than OSCCAL = 0x80.
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 9-15 on page
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
Bit
(0x66)
Read/Write
Initial Value
Bit
(0x61)
Read/Write
Initial Value
371. Calibration outside that range is not guaranteed.
Table 30-1 on page
CLKPCE
CAL7
R/W
R/W
7
7
0
51.
CAL6
R/W
6
R
6
–
0
ATmega640/1280/1281/2560/2561
371. The application software can write this register to change
CAL5
R/W
5
R
5
–
0
Device Specific Calibration Value
CAL4
R/W
4
R
4
–
0
CLKPS3
CAL3
R/W
R/W
3
3
CLKPS2
CAL2
See Bit Description
R/W
R/W
2
2
CLKPS1
CAL1
R/W
R/W
1
1
CLKPS0
CAL0
R/W
R/W
0
0
Table 30-
OSCCAL
CLKPR
50
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