ata6616 ATMEL Corporation, ata6616 Datasheet - Page 51

• Manufacturer Part Number: ata6616
• Description: Microcontroller With Lin Transceiver, 5v Regulator And Watchdog
• Manufacturer: ATMEL Corporation

4.5.2.1
4.5.2.2
9132A–AUTO–10/08
DRAFT
Default Clock Source
Calibrated Internal RC Oscillator
At reset, the CKSEL and SUT fuse settings are copied into the CLKSELR register. The device
will then use the clock source and the start-up timings defined by the CLKSELR bits (CSEL3..0
and CSUT1:0).
The device is shipped with CKSEL Fuses = 0010
grammed. The default clock source setting is therefore the Internal RC Oscillator running at 8
MHz with the longest start-up time and an initial system clock divided by 8. This default setting
ensures that all users can make their desired clock source setting using an In-System or
High-voltage Programmer. This set-up must be taken into account when using ISP tools.
By default, the Internal RC Oscillator provides an approximate 8.0 MHz clock. Though voltage
and temperature dependent, this clock can be accurately calibrated by the user. See
on page 269
If selected, it can operate without external components. At reset, hardware loads the pre-pro-
grammed calibration value into the OSCCAL Register and thereby automatically configuring the
RC Oscillator. The accuracy of this calibration is shown as Factory calibration in
page
By adjusting the OSCCAL register in software, see
bration Register” on page
factory calibration. The accuracy of this calibration is shown as User calibration in
page
The Watchdog Oscillator will still be used for the Watchdog Timer and for the Reset Time-out
even when this Oscillator is used as the device clock. For more information on the pre-pro-
grammed calibration value, see the section
Table 4-6.
Notes:
269.
269.
1. If 8 MHz frequency exceeds the specification of the device (depends on Vcc), the CKDIV8
2. The frequency ranges are guideline values
3. The device is shipped with this CKSEL = “0010”
4. Flash Fuse bits.
5. CLKSELR register bits
fuse can be programmed in order to divide the internal frequency by 8
and
Internal Calibrated RC Oscillator Operating Modes
Section 4.25.7 “Internal Oscillator Speed” on page 288
Frequency Range
62, it is possible to get a higher calibration accuracy than by using the
7.6 - 8.4
ATA6616/ATA6617 [Preliminary]
(2)
(MHz)
Section 4.22.4 “Calibration Byte” on page
b
, SUT Fuses = 10
Section 4.5.5.1 “OSCCAL – Oscillator Cali-
(1)
b
, and CKDIV8 Fuse pro-
for more details.
CKSEL3..0
CSEL3..0
0010
Table 4-80 on
Table 4-80 on
(5)
Table 4-80
(3)(4)
252.
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