Atmel ATtiny26 User Manual

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ATtiny26(L)
1477G–AVR–03/05
Clock Sources The device has the following clock source options, selectable by Flash Fuse bits as
shown below on Table 3. The clock from the selected source is input to the AVR clock
generator, and routed to the appropriate modules.The use of pins PB5 (XTAL2), and
PB4 (XTAL1) as I/O pins is limited depending on clock settings, as shown below in
Table 4.
Note: 1. For all fuses “1” means unprogrammed while “0” means programmed.
The various choices for each clocking option is given in the following sections. When the
CPU wakes up from Power-down, the selected clock source is used to time the start-up,
ensuring stable oscillator operation before instruction execution starts. When the CPU
starts from Reset, there is as an additional delay allowing the power to reach a stable
level before commencing normal operation. The Watchdog Oscillator is used for timing
this real-time part of the start-up time. The number of WDT Oscillator cycles used for
Table 3. Device Clocking Options Select
Device Clocking Option PLLCK CKSEL3..0
External Crystal/Ceramic Resonator 1 1111 - 1010
External Low-frequency Crystal 1 1001
External RC Oscillator 1 1000 - 0101
Calibrated Internal RC Oscillator 1 0100 - 0001
External Clock 1 0000
PLL Clock 0 0001
Table 4. PB5, and PB4 Functionality vs. Device Clocking Options
(1)
Device Clocking Option PLLCK CKSEL [3:0] PB4 PB5
External Clock 1 0000 XTAL1 I/O
Internal RC Oscillator 1 0001 I/O I/O
Internal RC Oscillator 1 0010 I/O I/O
Internal RC Oscillator 1 0011 I/O I/O
Internal RC Oscillator 1 0100 I/O I/O
External RC Oscillator 1 0101 XTAL1 I/O
External RC Oscillator 1 0110 XTAL1 I/O
External RC Oscillator 1 0111 XTAL1 I/O
External RC Oscillator 1 1000 XTAL1 I/O
External Low-frequency Oscillator 1 1001 XTAL1 XTAL2
External Crystal/Resonator Oscillator 1 1010 XTAL1 XTAL2
External Crystal/Resonator Oscillator 1 1011 XTAL1 XTAL2
External Crystal/Resonator Oscillator 1 1100 XTAL1 XTAL2
External Crystal/Resonator Oscillator 1 1101 XTAL1 XTAL2
External Crystal/Resonator Oscillator 1 1110 XTAL1 XTAL2
External Crystal/Resonator Oscillator 1 1111 XTAL1 XTAL2
PLL 0 0001 I/O I/O

Atmel ATtiny26 Specifications

General

Brand	Atmel
Model	ATtiny26
Category	Microcontrollers
Language	English