ATTINY20-MMH Atmel, ATTINY20-MMH Datasheet - Page 20
![MCU AVR 2KB FLASH 12MHZ 20QFN](/photos/30/99/309958/qfn-16_sml.jpg)
ATTINY20-MMH
Manufacturer Part Number
ATTINY20-MMH
Description
MCU AVR 2KB FLASH 12MHZ 20QFN
Manufacturer
Atmel
Series
AVR® ATtinyr
Datasheet
1.ATTINY20-EK1.pdf
(224 pages)
Specifications of ATTINY20-MMH
Core Processor
AVR
Core Size
8-Bit
Speed
12MHz
Connectivity
I²C, SPI
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
12
Program Memory Size
2KB (1K x 16)
Program Memory Type
FLASH
Ram Size
128 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
*
Processor Series
ATtiny
Core
AVR
Data Bus Width
8 bit
Data Ram Size
128 B
Interface Type
SPI, TWI
Maximum Clock Frequency
12 MHz
Number Of Programmable I/os
12
Number Of Timers
2
Operating Supply Voltage
3.3 V
Maximum Operating Temperature
+ 85 C
Mounting Style
SMD/SMT
Minimum Operating Temperature
- 40 C
Operating Temperature Range
- 40 C to + 85 C
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Eeprom Size
-
Lead Free Status / Rohs Status
Details
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
ATTINY20-MMHR
Manufacturer:
ATMEL
Quantity:
20 000
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6.2.3
6.2.4
6.2.5
6.3
6.3.1
6.4
6.4.1
20
System Clock Prescaler
Starting
ATtiny20
Internal 128 kHz Oscillator
Switching Clock Source
Default Clock Source
Switching Prescaler Setting
Starting from Reset
The internal 128 kHz oscillator is a low power oscillator providing a clock of 128 kHz. The fre-
quency depends on supply voltage, temperature and batch variations. This clock may be select
as the main clock by setting the CLKMS[1:0] bits in CLKMSR to 0b01.
The main clock source can be switched at run-time using the
Register” on page
that no glitch occurs in the main clock.
The calibrated internal 8 MHz oscillator is always selected as main clock when the device is
powered up or has been reset. The synchronous system clock is the main clock divided by 8,
controlled by the System Clock Prescaler. The Clock Prescaler Select Bits can be written later to
change the system clock frequency. See “System Clock Prescaler”.
The system clock is derived from the main clock via the System Clock Prescaler. The system
clock can be divided by setting the
tem clock prescaler can be used to decrease power consumption at times when requirements
for processing power is low or to bring the system clock within limits of maximum frequency. The
prescaler can be used with all main clock source options, and it will affect the clock frequency of
the CPU and all synchronous peripherals.
The System Clock Prescaler can be used to implement run-time changes of the internal clock
frequency while still ensuring stable operation.
When switching between prescaler settings, the system clock prescaler ensures that no glitch
occurs in the system clock and that no intermediate frequency is higher than neither the clock
frequency corresponding the previous setting, nor the clock frequency corresponding to the new
setting.
The ripple counter that implements the prescaler runs at the frequency of the main clock, which
may be faster than the CPU's clock frequency. Hence, it is not possible to determine the state of
the prescaler - even if it were readable, and the exact time it takes to switch from one clock divi-
sion to another cannot be exactly predicted.
From the time the CLKPS values are written, it takes between T1 + T2 and T1 + 2*T2 before the
new clock frequency is active. In this interval, two active clock edges are produced. Here, T1 is
the previous clock period, and T2 is the period corresponding to the new prescaler setting.
The internal reset is immediately asserted when a reset source goes active. The internal reset is
kept asserted until the reset source is released and the start-up sequence is completed. The
start-up sequence includes three steps, as follows.
1. The first step after the reset source has been released consists of the device counting
the reset start-up time. The purpose of this reset start-up time is to ensure that supply
22. When switching between any clock sources, the clock system ensures
“CLKPSR – Clock Prescale Register” on page
“CLKMSR – Clock Main Settings
8235B–AVR–04/11
22. The sys-
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