ATA6616 Datasheet, PDF (54/308 Pages) ATMEL Corporation – Single-package High Performance, Low Power AVR 8-bit Microcontroller with LIN

Figure 4-12. Low-frequency Crystal Oscillator Connections
C1 = 12 - 22pF
32.768KHz
C2 = 12 - 22pF
XTAL2
XTAL1
GND
12 - 22pF capacitors may be necessary if parasitic
impedance (pads, wires & PCB) is very low.
When this oscillator is selected, start-up times are determined by the SUT fuses or by CSUT
field as shown in Table 4-12.
Table 4-12. Start-up Times for the Low Frequency Crystal Oscillator Clock Selection
SUT1..0⁽¹⁾
CSUT1..0⁽²⁾
Start-up Time from Additional Delay from
Power-down/save Reset (Vcc = 5.0V)
Recommended Usage
00
1K (1024) CK⁽³⁾
01
1K (1024) CK⁽³⁾
4.1ms
65ms
Fast rising power or BOD enabled
Slowly rising power
10
32K (32768) CK
65ms
Stable frequency at start-up
11
Reserved
Notes: 1. Flash Fuse bits
2. CLKSELR register bits
3. These options should only be used if frequency stability at start-up is not important for the
application
4.5.2.6
External Clock
To drive the device from this external clock source, CLKI should be driven as shown in Figure
4-13. To run the device on an external clock, the CKSEL Fuses or CSEL field must be pro-
grammed as shown in Table 4-5 on page 49.
Figure 4-13. External Clock Drive Configuration
~
External
Clock
Signal
(XTAL2)
(CLKO)
CLKI
(XTAL1)
GND
When this clock source is selected, start-up times are determined by the SUT Fuses or CSUT
field as shown in Table 4-13 This external clock can be used by the asynchronous timer if the
high or low frequency Crystal Oscillator is not running (See ”Enable/Disable Clock Source” on
page 57.). The asynchronous timer is then able to enable this input.
54 Atmel ATA6616/ATA6617
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