AT89LP51RB2 datasheet(87/254 Pages) ATMEL

87 / 254 page

3722A–MICRO–10/11

AT89LP51RB2/RC2/IC2 Preliminary

Figure 13-10. Timer/Counter 0 PWM Mode 3

14. Timer 2

The AT89LP51RB2/RC2/IC2 includes a 16-bit Timer/Counter 2 with the following features:

• 16-bit timer/counter with one 16-bit reload/capture register

• One external reload/capture input

• Up/Down counting mode with external direction control

•UART baud rate generation

•Output-pin toggle on timer overflow

Timer 2 is a 16-bit Timer/Counter that can operate as either a timer or an event counter. The

type of operation is selected by bit C/T2 in the SFR T2CON. Timer 2 has three operating modes:

capture, auto-reload (up or down counting), and baud rate generator. The modes are selected

by bits in T2CON and T2MOD, as shown in Table 14-1.

Timer 2 consists of two 8-bit registers, TH2 and TL2. In the Timer function, the register is incre-

mented every clock cycle. The timer rate can be prescaled by a value between 1 and 16 using

the Timer Prescaler (see Section 6.9 on page 48). In Compatibility mode the prescaler is always

enabled and TPS defaults to 5, so Timer 2 counts every six clock cycles (1/12 of the oscillator

frequency in X1 mode or 1/6 of the oscillator frequency in X2 mode). In X2 mode Timer 2 can be

set to the X1 rate by setting the T2X2 bit in CKCON1. In Fast mode the prescaler is not enabled

by default so the count rate is equal to the system frequency (1/2 of the oscillator frequency in

X1 mode or equal to the oscillator frequency in X2 mode). In this case setting the T2X2 bit in

CKCON1 enables the prescaler for Timer 2.

Note that Timer 2 is not affected by the prescaler when operating in the Baud-Rate or Frequency

Generator modes.

CLKSYS

TR0

GATE0

INT0 Pin

Control

TL0

(8 Bits)

OCR0

RL0

(8 Bits)

CLKSYS

TH0

(8 Bits)

OCR1

RH0

(8 Bits)

TR1

÷TPS

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