P89LPC932 datasheet(18/60 Pages) PHILIPS

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Philips Semiconductors

P89LPC932

8-bit microcontroller with accelerated two-clock 80C51 core

Product data

Rev. 04 — 06 January 2004

18 of 60

9397 750 12379

8.2.6

Clock output

The P89LPC932 supports a user-selectable clock output function on the

XTAL2/CLKOUT pin when crystal oscillator is not being used. This condition occurs if

another clock source has been selected (on-chip RC oscillator, watchdog oscillator,

external clock input on X1) and if the Real-Time clock is not using the crystal

oscillator as its clock source. This allows external devices to synchronize to the

P89LPC932. This output is enabled by the ENCLK bit in the TRIM register.

The frequency of this clock output is 1

⁄

2 that of the CCLK. If the clock output is not

needed in Idle mode, it may be turned off prior to entering Idle, saving additional

power.

8.3 On-chip RC oscillator option

The P89LPC932 has a 6-bit TRIM register that can be used to tune the frequency of

the RC oscillator. During reset, the TRIM value is initialized to a factory

pre-programmed value to adjust the oscillator frequency to 7.373 MHz,

±2.5 %.

End-user applications can write to the TRIM register to adjust the on-chip RC

oscillator to other frequencies.

8.4 Watchdog oscillator option

The watchdog has a separate oscillator which has a frequency of 400 kHz. This

oscillator can be used to save power when a high clock frequency is not needed.

8.5 External clock input option

In this conﬁguration, the processor clock is derived from an external source driving

the XTAL1/P3.1 pin. The rate may be from 0 Hz up to 12 MHz. The XTAL2/P3.0 pin

may be used as a standard port pin or a clock output.

Fig 6.

Block diagram of oscillator control.

÷2

002aaa515

RTC

CPU

WDT

DIVM

CCLK

UART

OSCCLK

I2C

PCLK

TIMER 0 and

TIMER 1

High freq.

Med. freq.

Low freq.

XTAL1

XTAL2

OSCILLATOR

WATCHDOG

OSCILLATOR

(7.3728 MHz ±2.5%)

(400 kHz +20% -30%)

PCLK

RCCLK

SPI

CCU

× PLL

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