ata6616 ATMEL Corporation, ata6616 Datasheet - Page 121

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

4.11.9
9132A–AUTO–10/08
DRAFT
Asynchronous Operation of Timer/Counter0
Figure 4-39
Figure 4-39. Timer/Counter Timing Diagram, Setting of OCF0A, with Prescaler (f
Figure 4-40
Figure 4-40. Timer/Counter Timing Diagram, Clear Timer on Compare Match mode, with Pres-
When Timer/Counter0 operates asynchronously, some considerations must be taken.
• Warning: When switching between asynchronous and synchronous clocking of
• If an 32.768 kHz watch crystal is used, the CPU main clock frequency must be more than
Timer/Counter0, the timer registers TCNT0, OCR0A, and TCCR0A might be corrupted. A
safe procedure for switching clock source is:
a) Disable the Timer/Counter0 interrupts by clearing OCIE0A and TOIE0.
b) Select clock source by setting AS0 and EXCLK as appropriate.
c) Write new values to TCNT0, OCR0A, and TCCR0A.
d) To switch to asynchronous operation: Wait for TCN0UB, OCR0UB, and TCR0UB.
e) Clear the Timer/Counter0 interrupt flags.
f) Enable interrupts, if needed.
four times the Oscillator or external clock frequency.
TCNTn
(clk
(CTC)
OCRnx
OCFnx
clk
clk
I/O
I/O
Tn
/8)
shows the setting of OCF0A in all modes except CTC mode.
shows the setting of OCF0A and the clearing of TCNT0 in CTC mode.
TCNTn
OCRnx
OCFnx
(clk
clk
clk
caler (f
I/O
I/O
Tn
/8)
clk_I/O
TOP - 1
OCRnx - 1
/8)
ATA6616/ATA6617 [Preliminary]
OCRnx
TOP
OCRnx Value
TOP
OCRnx + 1
BOTTOM
OCRnx + 2
BOTTOM + 1
clk_I/O
/8)
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