ATA6602-PLQW ATMEL [ATMEL Corporation], ATA6602-PLQW Datasheet - Page 55

• Manufacturer Part Number: ATA6602-PLQW
• Description: Microcontroller with LIN Transceiver, 5V Regulator and Watchdog
• Manufacturer: ATMEL [ATMEL Corporation]

4.6.6.1
4.6.7
4921C–AUTO–01/07
128 kHz Internal Oscillator
Oscillator Calibration Register – OSCCAL
The 128 kHz internal Oscillator is a low power Oscillator providing a clock of 128 kHz. The fre-
quency is nominal at 3V and 25 C. This clock may be select as the system clock by
programming the CKSEL Fuses to “11” as shown in
Table 4-13.
Note:
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table 4-14 on page
• Bits 7..0 – CAL7..0: Oscillator Calibration Value
Initial Value
Read/Write
The Oscillator Calibration Register is used to trim the Calibrated Internal RC Oscillator to
remove process variations from the oscillator frequency. The factory-calibrated value is
automatically written to this register during chip reset, giving an oscillator frequency of
8.0 MHz at 25°C. The application software can write this register to change the oscillator fre-
quency. The oscillator can be calibrated to any frequency in the range 7.3 - 8.1 MHz within
±1% accuracy. Calibration outside that range is not guaranteed.
Note that this oscillator is used to time EEPROM and Flash write accesses, and these write
times will be affected accordingly. If the EEPROM or Flash are written, do not calibrate to
more than 8.8 MHz. Otherwise, the EEPROM or Flash write may fail.
The CAL7 bit determines the range of operation for the oscillator. Setting this bit to 0 gives
the lowest frequency range, setting this bit to 1 gives the highest frequency range. The two
frequency ranges are overlapping, in other words a setting of OSCCAL = 0x7F gives a
higher frequency than OSCCAL = 0x80.
The CAL6..0 bits are used to tune the frequency within the selected range. A setting of 0x00
gives the lowest frequency in that range, and a setting of 0x7F gives the highest frequency
in the range. Incrementing CAL6..0 by 1 will give a frequency increment of less than 2% in
the frequency range 7.3 - 8.1 MHz.
Bit
1. The frequency is preliminary value. Actual value is TBD.
128 kHz Internal Oscillator Operating Modes
CAL7
R/W
7
Nominal Frequency
56.
CAL6
R/W
128 kHz
6
CAL5
R/W
5
Device Specific Calibration Value
CAL4
R/W
4
CAL3
R/W
Table
3
4-13.
ATA6602/ATA6603
CAL2
R/W
2
CAL1
R/W
1
CKSEL3..0
0011
CAL0
R/W
0
OSCCAL
55