ATAR080 datasheet(31/68 Pages) ATMEL

31 / 68 page

ATAR080

4675D–4BMCU–12/04

Its output has a modulator stage that allows the generation of pulses as well as the gen-

eration and modulation of carrier frequencies. Timer 2 output can modulate with the shift

If the serial interface is used to modulate a bit-stream, the 4-bit stage of Timer 2 has a

special task. The shift register can only handle bit-stream lengths divisible by 8. For

other lengths, the 4-bit counter stage can be used to stop the modulator after the right

bit-count is shifted out.

If the timer is used for carrier frequency modulation, the 4-bit stage works together with

an additional 2-bit duty cycle generator like a 6-bit prescaler to generate carrier fre-

quency and duty cycle. The 8-bit counter is used to enable and disable the modulator

output for a programmable count of pulses.

The timer has a 4-bit and an 8-bit compare register for programming the time interval.

For programming the timer function, it has four mode and control registers. The compar-

ator output of stage 2 is controlled by a special compare mode register (T2CM). This

which can be triggered by a compare match event or the counter overflow. This archi-

tecture enables the timer to function for various modes.

Timer 2 compare data values

Timer 2 has a 4-bit compare register (T2CO1) and an 8-bit compare register (T2CO2).

Both these compare registers are cascadable as a 12-bit compare register, or 8-bit com-

pare register and 4-bit compare register.

•

For 12-bit compare data value: m = x + 1; 0

≤x ≤4095

•

For 8-bit compare data value: n = y + 1; 0

≤y ≤255

•

For 4-bit compare data value: l = z +1; 0

≤z ≤15

Figure 29. Timer 2

4-bit Counter 2/1

RES

OVF1

Compare 2/1

T2CO1

CM1

POUT

SSI POUT

CL2/2

DCG

T2M1

P4CR

8-bit Counter 2/2

RES

OVF2

Compare 2/2

T2CO2

T2CM

Control

TOG2

INT4

Bi-phase

Manchester

Modulator

OUTPUT

MOUT

Modulator 3

T2O

Timer 2

modulator

output-stage

T2M2

Control

SSI

I/O-bus

T2C

CL2/1

T2I

SYSCL

T1OUT

SCL

I/O-bus

DCGO

ATAR080 Datasheet(PDF) 31 Page - ATMEL Corporation

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