ATtiny44 datasheet(89/236 Pages) ATMEL

89 / 236 page

8006H–AVR–10/09

ATtiny24/44/84

12.2.3

Compatibility

The 16-bit Timer/Counter has been updated and improved from previous versions of 16-bit AVR

Timer/Counters. This 16-bit Timer/Counter is fully compatible with the earlier version regarding:

• All 16-bit Timer/Counter related I/O Register address locations, including Timer Interrupt

Registers.

• Bit locations inside all 16-bit Timer/Counter Registers, including Timer Interrupt Registers.

• Interrupt Vectors.

The following control bits have changed name, but have same functionality and register location:

•PWM10 is changed to WGM10.

•PWM11 is changed to WGM11.

• CTC1 is changed to WGM12.

The following bits are added to the 16-bit Timer/Counter Control Registers:

• 1A and 1B are added to TCCR1A.

• WGM13 is added to TCCR1B.

The 16-bit Timer/Counter has improvements that will affect backward compatibility in some spe-

cial cases.

12.3

Timer/Counter Clock Sources

The Timer/Counter can be clocked by an internal or an external clock source. The clock source

is selected by the Clock Select logic which is controlled by the Clock Select (CS12:0) bits

located in the Timer/Counter control Register B (TCCR1B). For details on clock sources and

prescaler, see “Timer/Counter Prescaler” on page 115.

12.4

Counter Unit

The main part of the 16-bit Timer/Counter is the programmable 16-bit bi-directional counter unit.

Figure 12-2 on page 89 shows a block diagram of the counter and its surroundings.

Figure 12-2. Counter Unit Block Diagram

TEMP (8-bit)

DATA BUS (8-bit)

TCNTn (16-bit Counter)

TCNTnH (8-bit)

TCNTnL (8-bit)

Control Logic

Count

Clear

Direction

TOVn

(Int.Req.)

Clock Select

TOP

BOTTOM

Edge

Detector

( From Prescaler )

clk

ATtiny44 Datasheet(PDF) 89 Page - ATMEL Corporation

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