Rainbow Electronics ATtiny12 - Manual (Page 6)

6
ATtiny11/12
1006C–09/01
Note: “1” means unprogrammed, “0” means programmed.
The various choices for each clocking option give different start-up times as shown in
Table 7 on page 18 and Table 9 on page 20.
Internal RC Oscillator The internal RC oscillator option is an on-chip oscillator running at a fixed frequency of 1
MHz in ATtiny11 and 1.2 MHz in ATtiny12. If selected, the device can operate with no
external components. The device is shipped with this option selected. On ATtiny11, the
Watchdog Oscillator is used as a clock, while ATtiny12 uses a separate calibrated
oscillator.
Crystal Oscillator XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which can
be configured for use as an on-chip oscillator, as shown in Figure 3. Either a quartz
crystal or a ceramic resonator may be used. Maximum frequency for crystal and resona-
tors is 4 MHz. Minimum voltage for running on a low-frequency crystal is 2.5V.
Figure 3. Oscillator Connections
Note: When using the MCU Oscillator as a clock for an external device, an HC buffer should be
connected as indicated in the figure.
External Clock To drive the device from an external clock source, XTAL1 should be driven as shown in
Figure 4.
Figure 4. External Clock Drive Configuration
Internal RC Oscillator 100 0100 - 0010
External Clock 000 0001 - 0000
Reserved Other Options -
Table 3. Device Clocking Options Select (Continued)
Device Clocking Option ATtiny11 CKSEL2..0 ATtiny12 CKSEL3..0
XTAL2
XTAL1
GND
C2
C1
MAX 1 HC BUFFER
HC
PB4 (XTAL2)
XTAL1
GND
EXTERNAL
OSCILLATOR
SIGNAL