107
2513L–AVR–03/2013
ATmega162/V
Figure 46. 16-bit Timer/Counter Block Diagram
Note:
Timer/Counter1 pin placement and description.
Registers
The Timer/Counter (TCNTn), Output Compare Registers (OCRnA/B), and Input Capture Regis-
ter (ICRn) are all 16-bit registers. Special procedures must be followed when accessing the 16-
page 109. The Timer/Counter Control Registers (TCCRnA/B) are 8-bit registers and have no
CPU access restrictions. Interrupt requests (abbreviated to Int.Req. in the figure) signals are all
visible in the Timer Interrupt Flag Register (TIFR) and Extended Timer Interrupt Flag Register
(ETIFR). All interrupts are individually masked with the Timer Interrupt Mask Register (TIMSK)
and Extended Timer Interrupt Mask Register (ETIMSK). (E)TIFR and (E)TIMSK are not shown in
the figure since these registers are shared by other Timer units.
The Timer/Counter can be clocked internally, via the prescaler, or by an external clock source on
the T1 pin. The Clock Select logic block controls which clock source and edge the Timer/Counter
uses to increment (or decrement) its value. The Timer/Counter is inactive when no clock source
is selected. The output from the Clock Select logic is referred to as the Timer Clock (clk
Tn).
The double buffered Output Compare Registers (OCRnA/B) are compared with the Timer/Coun-
ter value at all time. The result of the compare can be used by the waveform generator to
generate a PWM or variable frequency output on the Output Compare pin (OCnA/B).
See “Out-Flag (OCFnA/B) which can be used to generate an output compare interrupt request.
Clock Select
Timer/Counter
DATABUS
OCRnA
OCRnB
ICRn
=
TCNTn
Waveform
Generation
Waveform
Generation
OCnA
OCnB
Noise
Canceler
ICPn
=
Fixed
TOP
Values
Edge
Detector
Control Logic
= 0
TOP
BOTTOM
Count
Clear
Direction
TOVn
(Int.Req.)
OCnA
(Int.Req.)
OCnB
(Int.Req.)
ICFn (Int.Req.)
TCCRnA
TCCRnB
( From Analog
Comparator Ouput )
Tn
Edge
Detector
( From Prescaler )
clk
Tn