P83C434CFP View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

P83C434CFP

8-bit microcontrollers with LCD-driver

Philips Electronics 

Philips Semiconductors

8-bit microcontrollers with LCD-driver

Product specification

P83C434; P83C834

6.2 Oscillator

6.2.1 CPU CLOCK

The internal timing circuits of the CPU are clocked by a

Current Controlled Oscillator (CCO). The oscillator is free

running and is adjusted by means of the Oscillator Control

Register (OSCON; see Section 6.6.4) and a

digital-to-analog converter; it does not require external

components. The frequency of the CPU clock can be

measured by means of Timer T0 which is clocked by the

32 kHz oscillator (see Section 6.2.2).

Adjustments can be made by changing the contents of the

OSCON register (see Fig.9). Over the range 0 to 31 the

frequency step size is constant (deviation ≤10%).

The frequency variation per step of the register is:

0.5 MHz < step size < 2 MHz.

At Power-on-reset the oscillator frequency will be:

1 MHz < fOSC < 4 MHz. Stability of the oscillator:

frequency change with time ≤1.5%. The maximum

operating frequency is: ≤12 MHz at VDD ≥4.5 V.

The minimum operating frequency is 1 MHz.

In Power-down mode the oscillator is stopped.

Table 3 Oscillator status during Power-down mode

RUN32

HIGH

LOW

32 kHz OSCILLATOR

running

stopped

6.2.3 15-BIT COUNTER (1-SECOND TIMER)

An interrupt is generated every second by the 15-bit

counter. This 1-second timer is a 15-bit counter, clocked

by the 32 kHz oscillator output. When this counter

overflows it generates an INT1 interrupt by setting SECINT

in the Miscellaneous Control Register (MCON). Reset of

this interrupt is carried out via software by clearing bit

SECINT.

handbook, halfpage

XTAL1

XTAL2

6.2.2 LCD DRIVER CLOCK: 32 KHZ OSCILLATOR

A 32 kHz oscillator provides the clocking of the LCD timing

generator and may also be used as the time base for a

Real Time Clock. The output of the 32 kHz oscillator is also

used as an input of Timer/Counter 0.

The frequency of the 32 kHz oscillator need not be exactly

32 kHz, and is determined by the component(s) connected

between pins XTAL1 and XTAL2. See Chapter 11.

The oscillator is suitable for use with either:

• A crystal; connected as shown in Fig.6a

• External drive; connected as shown in Fig.6b.

During Power-down mode, the control bit RUN32 in the

Miscellaneous Control Register (MCON) determines

whether the oscillator is stopped or running continuously;

see Table 3.

The output of the oscillator (XTAL2) is used as an input to

the Timer/Counter 0. This can be useful for accurate time

measurements and generation of time-slots. For example

it may be used to determine (and possibly adjust) the

frequency of the CCO that is used for the CPU clock.

MLC928

a. Crystal oscillator.

handbook, halfpage

XTAL1

XTAL2

n.c.

external clock

(not TTL compatible)

MBE312

b. External clock drive.

Fig.6 Oscillator configurations P83C434/P83C834.

1997 Jul 03

9

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