AT90CAN64 datasheet(41/428 Pages) ATMEL

41 / 428 page

7679H–CAN–08/08

AT90CAN32/64/128

When this Oscillator is selected, start-up times are determined by the SUT1..0 fuses as shown in

Table 5-5 and CKSEL1..0 fuses as shown in Table 5-6.

Note:

1. These options should only be used if frequency stability at start-up is not important for the

application

5.6

Calibrated Internal RC Oscillator

The calibrated internal RC Oscillator provides a fixed 8.0 MHz clock. The frequency is nominal

value at 3V and 25

°C. If 8 MHz frequency exceeds the specification of the device (depends on

CC), the CKDIV8 Fuse must be programmed in order to divide the internal frequency by 8 dur-

ing start-up. The device is shipped with the CKDIV8 Fuse programmed. See “System Clock

Prescaler” on page 44. for more details. This clock may be selected as the system clock by pro-

gramming the CKSEL Fuses as shown in Table 5-7. If selected, it will operate with no external

components. During reset, hardware loads the calibration byte into the OSCCAL Register and

thereby automatically calibrates the RC Oscillator. At 5V and 25

°C, this calibration gives a fre-

quency within ± 10% of the nominal frequency. Using calibration methods as described in

application notes available at www.atmel.com/avr it is possible to achieve ± 2% accuracy at any

given VCC and temperature. When this Oscillator is used as the chip clock, the Watchdog Oscil-

lator will still be used for the Watchdog Timer and for the Reset Time-out. For more information

on the pre-programmed calibration value, see the section “Calibration Byte” on page 339.

Note:

1. The device is shipped with this option selected.

Table 5-5.

Start-up Times for the Low-frequency Crystal Oscillator Clock Selection

SUT1..0

Additional Delay from Reset (V

CC = 5.0V)

Recommended Usage

14 CK

Fast rising power or BOD enabled

14 CK + 4.1 ms

Slowly rising power

14 CK + 65 ms

Stable frequency at start-up

Reserved

Table 5-6.

Start-up Times for the Low-frequency Crystal Oscillator Clock Selection

CKSEL3..0

Start-up Time from

Power-down and Power-save

Recommended Usage

0100(1)

1K CK

0101

32K CK

Stable frequency at start-up

0110(1)

1K CK

0111

32K CK

Stable frequency at start-up

Table 5-7.

Internal Calibrated RC Oscillator Operating Modes

(1)

CKSEL3..0

Nominal Frequency

0010

8.0 MHz

AT90CAN64 Datasheet(PDF) 41 Page - ATMEL Corporation

AT90CAN64 Datasheet(HTML) 41 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL