ATAR080 datasheet(32/68 Pages) ATMEL

32 / 68 page

ATAR080

4675D–4BMCU–12/04

Timer 2 Modes

Mode 1: 12-bit Compare Counter

The 4-bit stage and the 8-bit stage work together as a 12-bit compare counter. A com-

pare match signal of the 4-bit and the 8-bit stage generates the signal for the counter

reset, toggle flip-flop or interrupt. The compare action is programmable via the compare

mode register (T2CM). The 4-bit counter overflow (OVF1) supplies the clock output

(POUT) with clocks. The duty cycle generator (DCG) has to be bypassed in this mode.

Figure 30. 12-bit Compare Counter

Mode 2: 8-bit Compare Counter with 4-bit Programmable Prescaler

The 4-bit stage is used as a programmable prescaler for the 8-bit counter stage. In this

mode, a duty cycle stage is also available. This stage can be used as an additional 2-bit

prescaler or for generating duty cycles of 25%, 33% and 50%. The 4-bit compare output

(CM1) supplies the clock output (POUT) with clocks.

Figure 31. 8-bit Compare Counter

Mode 3/4: 8-bit Compare Counter and 4-bit Programmable Prescaler

In these modes the 4-bit and the 8-bit counter stages work independently as a 4-bit

prescaler and an 8-bit timer with a 2-bit prescaler or as a duty cycle generator. Only in

mode 3 and mode 4 can the 8-bit counter be supplied via the external clock input (T2I)

which is selected via the P4CR register. The 4-bit prescaler is started by activating

mode 3 and stopped and reset in mode 4. Changing mode 3 and 4 has no effect for the

8-bit timer stage. The 4-bit stage can be used as a prescaler for the SSI or to generate

the stop signal for modulator 2.

4-bit counter

4-bit compare

RES

4-bit register

CM1

POUT (CL2/1/16)

8-bit counter

8-bit compare

8-bit register

OVF2

CM2

RES

T2RM

T2OTM

Timer 2

output mode

and T2OTM-bit

T2IM

T2CTM

TOG2

INT4

CL2/1

DCG

T2D1, 0

4-bit counter

4-bit compare

RES

4-bit register

CM1

POUT

8-bit counter

8-bit compare

8-bit register

OVF2

CM2

RES

T2RM

T2OTM

Timer 2

output mode

and T2OTM-bit

T2IM

T2CTM

TOG2

INT4

CL2/1

DCG

T2D1, 0

DCGO

ATAR080 Datasheet(PDF) 32 Page - ATMEL Corporation

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