ATTINY261-20MU Atmel, ATTINY261-20MU Datasheet - Page 34

• Manufacturer Part Number: ATTINY261-20MU
• Description: IC MCU AVR 2K FLASH 20MHZ 32-QFN
• Manufacturer: Atmel
• Series: AVR® ATtinyr

Specifications of ATTINY261-20MU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 16
• Program Memory Size: 2KB (1K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 128 x 8
• Ram Size: 128 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 11x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-VQFN Exposed Pad, 32-HVQFN, 32-SQFN, 32-DHVQFN
• Processor Series: ATTINY2x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 128 B
• Interface Type: 2-Wire, SPI, USI
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 16
• Number Of Timers: 2
• 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
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 10 bit, 11 Channel
• Package: 32MLF EP
• Device Core: AVR
• Family Name: ATtiny
• Maximum Speed: 20 MHz
• Operating Supply Voltage: 3.3|5 V
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32ATAVRBC100 - REF DESIGN KIT BATTERY CHARGER770-1007 - ISP 4PORT ATMEL AVR MCU SPI/JTAGATSTK505 - ADAPTER KIT FOR 14PIN AVR MCU
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

34
ATtiny261/461/861
• Bits 6:4 – Res: Reserved Bits
These bits are reserved and will always read as zero.
• 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
To avoid unintentional changes of clock frequency, a special write procedure must be followed
to change the CLKPS bits:
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 eight 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
operating 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 selcted 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 6-13.
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.
CLKPS3
CLKPR to zero.
6-13.
0
0
0
0
0
0
0
0
1
1
1
1
1
Clock Prescaler Select
CLKPS2
0
0
0
0
1
1
1
1
0
0
0
0
1
CLKPS1
0
0
1
1
0
0
1
1
0
0
1
1
0
CLKPS0
0
1
0
1
0
1
0
1
0
1
0
1
0
Clock Division Factor
Reserved
Reserved
Reserved
Reserved
128
256
16
32
64
1
2
4
8
2588E–AVR–08/10