ATA6616 Datasheet, PDF (140/308 Pages) ATMEL Corporation – Single-package High Performance, Low Power AVR 8-bit Microcontroller with LIN

The counting sequence is determined by the setting of the Waveform Generation mode bits
(WGM13:0) located in the Timer/Counter Control Registers A and B (TCCR1A and TCCR1B).
There are close connections between how the counter behaves (counts) and how waveforms
are generated on the Output Compare outputs OC1A/B. For more details about advanced
counting sequences and waveform generation, see “Modes of Operation” on page 147.
The Timer/Counter Overflow Flag (TOV1) is set according to the mode of operation selected
by the WGM13:0 bits. TOV1 can be used for generating a CPU interrupt.
4.13.6
Input Capture Unit
The Timer/Counter incorporates an Input Capture unit that can capture external events and
give them a time-stamp indicating time of occurrence. The external signal indicating an event,
or multiple events, can be applied via the ICP1 pin or alternatively, via the analog-comparator
unit. The time-stamps can then be used to calculate frequency, duty-cycle, and other features
of the signal applied. Alternatively the time-stamps can be used for creating a log of the
events.
The Input Capture unit is illustrated by the block diagram shown in Figure 4-46. The elements
of the block diagram that are not directly a part of the Input Capture unit are gray shaded.
Figure 4-46. Input Capture Unit Block Diagram
DATA BUS (8-bit)
TEMP (8-bit)
ICRnH (8-bit)
ICRnL (8-bit)
WRITE
ICRn (16-bit Register)
TCNTnH (8-bit)
TCNTnL (8-bit)
TCNTn (16-bit Counter)
ICPn
ACO
Analog
Comparator
ACIC
ICNCn
Noise
Canceler
ICESn
Edge
Detector
ICF1n (Int.Req.)
When a change of the logic level (an event) occurs on the Input Capture pin (ICP1), alterna-
tively on the Analog Comparator output (ACO), and this change confirms to the setting of the
edge detector, a capture will be triggered. When a capture is triggered, the 16-bit value of the
counter (TCNT1) is written to the Input Capture Register (ICR1). The Input Capture Flag
(ICF1) is set at the same system clock as the TCNT1 value is copied into ICR1 Register. If
enabled (ICIE1 = 1), the Input Capture Flag generates an Input Capture interrupt. The ICF1
flag is automatically cleared when the interrupt is executed. Alternatively the ICF1 flag can be
cleared by software by writing a logical one to its I/O bit location.
140 Atmel ATA6616/ATA6617
9132D–AUTO–12/10