ATA6602 ATMEL Corporation, ATA6602 Datasheet - Page 320

• Manufacturer Part Number: ATA6602
• Description: LIN and Microcontroller System-In-Package: LIN Transceiver, integrated 5V/50 mA voltage regulator, window watchdog and automotive AVR ATmega88 (8 kBytes Flash); green QFN48 package.
• Manufacturer: ATMEL Corporation

4.26
4.26.1
4.26.2
320
LIN Re-synchronization Algorithm
ATA6602/ATA6603
Synchronization Algorithm
Precaution Against OSCCAL Discontinuity
The possibility to change the value of OSCCAL during the Oscillator operation allows for in-situ
calibration of the slave node to entering Master frames. The principle of operation is to measure
the TBit during the SYNCH Byte and to change the calibration value of OSCCAL to recover from
local frequency drifts due to local voltage or temperature deviation. The algorithm used for the
synchronization of the internal RC oscillator is depicted in
Figure 4-130. Dichotomic Algorithm Used for LIN Slave Clock Re-synchronization
The
OSCCAL value. For one correct re-synchronization, the frequency change must be kept on the
same side of the discontinuity (no change of OSCCAL[7]). Since there will be no device having
frequency changed by more than 10% (see
change the frequency value by more than 10%. Therefore, when calibration tries to cross the
border because of subsequent increase (or decrease) in OSCCAL values, then the routine must
be stopped.
Example: For parts operating in the lower part of the curve, if New_OSCCAL >127 then
New_OSCCAL = 127. Similar for parts operating on the high side of the discontinuity.
Figure 5-26 on page 337
Decrement
Increment
OSCCAL
OSCCAL
illustrates the on-purpose discontinuity of RC Frequency versus
-2% < Delta(TBit) < 2%
Delta(TBit) > 2%
Delta(TBit) < -2%
Measuring
actual TBit
Figure 5-24 on page
N
N
Figure
Y
4-130.
STOP:
Oscillator
Calibrated
336), thus no reason to
4921C–AUTO–01/07