MEGA128CAN Datasheet, PDF (37/413 Pages) ATMEL Corporation – Microcontroller WITH 128K BYTES OF ISP FLASH AND CAN CONTROLLER

Low-frequency
Crystal Oscillator
AT90CAN128
Table 8. Start-up Times for the Oscillator Clock Selection
CKSEL0 SUT1..0
0
00
Start-up Time from
Power-down and
Power-save
258 CK⁽¹⁾
0
01
258 CK⁽¹⁾
0
10
1K CK⁽²⁾
0
11
1K CK⁽²⁾
1
00
1K CK⁽²⁾
Additional Delay
from Reset
(V_CC = 5.0V)
14CK + 4.1 ms
14CK + 65 ms
14CK
14CK + 4.1 ms
14CK + 65 ms
Recommended Usage
Ceramic resonator, fast
rising power
Ceramic resonator,
slowly rising power
Ceramic resonator,
BOD enabled
Ceramic resonator, fast
rising power
Ceramic resonator,
slowly rising power
1
01
16K CK
14CK
Crystal Oscillator, BOD
enabled
1
10
16K CK
14CK + 4.1 ms
Crystal Oscillator, fast
rising power
1
11
16K CK
14CK + 65 ms
Crystal Oscillator,
slowly rising power
Notes:
1. These options should only be used when not operating close to the maximum fre-
quency of the device, and only if frequency stability at start-up is not important for the
application. These options are not suitable for crystals.
2. These options are intended for use with ceramic resonators and will ensure fre-
quency stability at start-up. They can also be used with crystals when not operating
close to the maximum frequency of the device, and if frequency stability at start-up is
not important for the application.
To use a 32.768 kHz watch crystal as the clock source for the device, the low-frequency
crystal Oscillator must be selected by setting the CKSEL Fuses to “0100”, “0101”,
“0110”, or “0111”. The crystal should be connected as shown in Figure 21.
Figure 21. Low-frequency Crystal Oscillator Connections
12 - 22 pF
32.768 KHz
12 - 22 pF
XTAL2
XTAL1
GND
12-22 pF capacitors may be necessary if the parasitic impedance (pads, wires & PCB)
is very low.
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4250E–CAN–12/04