T48C893 datasheet(34/82 Pages) ATMEL

34 / 82 page

T48C893

Rev. A4, 22-Jan-02

34 (82)

Mode 2: 8-bit compare counter with 4-bit programmable prescaler

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

13778

DCG

T2D1, 0

DCGO

Figure 32. 8-bit compare counter

The 4-bit stage is used as 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.

Mode 3/4: 8-bit compare counter and 4-bit programmable prescaler

4-bit counter

4-bit compare

RES

4-bit register

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

CL2/2

13779

DCG

T2D1, 0

DCGO

P41M2, 1

P4CR

CM1

POUT

CL2/1

MUX

TOG3

T1OUT

SYSCL

SCL

T2CS1, 0

SYSCL

T2I

Figure 33. 4-/8-bit compare counter

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

an 2-bit prescaler or as a duty cycle generator. Only in the

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 via activating

of 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 prescaler for Timer 3, the SSI

or to generate the stop signal for modulator 2 and

modulator 3.

Timer 2 Output Modes

The signal at the timer output is generated via

modulator 2. In the toggle mode, the compare match

event toggles the output T2O. For high resolution duty

cycle modulation 8 bits or 12 bits can be used to toggle the

output. In the duty cycle burst modulator modes the DCG

T48C893 Datasheet(PDF) 34 Page - ATMEL Corporation

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