AT89LP213 datasheet(28/98 Pages) ATMEL

28 / 98 page

3538D–MICRO–10/09

AT89LP213/214

14. Enhanced Timer/Counters

The AT89LP213/214 has two 16-bit Timer/Counter registers: Timer 0 and Timer 1. As a Timer,

the register increase every clock cycle by default. Thus, the register counts clock cycles. Since a

clock cycle consists of one oscillator period, the count rate is equal to the oscillator frequency.

The timer rate can be prescaled by a value between 1 and 16 using the Timer Prescaler (see

Table 9-2 on page 14). Both Timers share the same prescaler.

As a Counter, the register is incremented in response to a l-to-0 transition at its corresponding

input pin, T0 or T1. The external input is sampled every clock cycle. When the samples show a

high in one cycle and a low in the next cycle, the count is incremented. The new count value

appears in the register during the cycle following the one in which the transition was detected.

Since 2 clock cycles are required to recognize a l-to-0 transition, the maximum count rate is 1/2

of the oscillator frequency. There are no restrictions on the duty cycle of the input signal, but it

should be held for at least one full clock cycle to ensure that a given level is sampled at least

once before it changes. In the AT89LP214, the T0 and T1 inputs are not available at the pins.

Table 13-5.

Port Pin Alternate Functions

Port Pin

Configuration Bits

Alternate

Function

Notes

PxM0.y

PxM1.y

P1.0

P1M0.0

P1M1.0

AIN0

input-only

GPI0

P1.1

P1M0.1

P1M1.1

AIN1

input-only

GPI1

P1.2

P1M0.2

P1M1.2

GPI2

P1.3

P1M0.3

P1M1.3

GPI3

RST must be disabled

P1.4

P1M0.4

P1M1.4

Resets to quasi-bidirectional

GPI4

P1.5

P1M0.5

P1M1.5

MOSI

GPI5

P1.6

P1M0.6

P1M1.6

MISO

GPI6

P1.7

P1M0.7

P1M1.7

SCK

GPI7

P3.0

P3M0.0

P3M1.0

RXD

AT89LP214 Only

Set as output on AT89LP213

P3.1

P3M0.1

P3M1.1

TXD

P3.2

P3M0.2

P3M1.2

INT0

Internal RC Oscillator Only

P3.3

P3M0.3

P3M1.3

INT1

Internal RC Oscillator or

External Clock Source Only

CLKOUT

P3.4

P3M0.4

P3M1.4

AT89LP213 Only

Set as output on AT89LP214

P3.5

P3M0.5

P3M1.5

P3.6

not configurable

CMPOUT

Pin is tied to comparator output

AT89LP213 Datasheet(PDF) 28 Page - ATMEL Corporation

AT89LP213 Datasheet(HTML) 28 Page - ATMEL Corporation

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