P89LPC933FDH datasheet(24/75 Pages) PHILIPS

24 / 75 page

9397 750 15113

Product data sheet

Rev. 06 — 20 June 2005

24 of 75

Philips Semiconductors

P89LPC933/934/935/936

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

8.2 Enhanced CPU

The P89LPC933/934/935/936 uses an enhanced 80C51 CPU which runs at six times the

speed of standard 80C51 devices. A machine cycle consists of two CPU clock cycles, and

most instructions execute in one or two machine cycles.

8.3 Clocks

8.3.1 Clock deﬁnitions

The P89LPC933/934/935/936 device has several internal clocks as deﬁned below:

OSCCLK — Input to the DIVM clock divider. OSCCLK is selected from one of four clock

sources (see Figure 8) and can also be optionally divided to a slower frequency (see

Section 8.8 “CCLK modiﬁcation: DIVM register”).

Remark: fosc is deﬁned as the OSCCLK frequency.

CCLK — CPU clock; output of the clock divider. There are two CCLK cycles per machine

cycle, and most instructions are executed in one to two machine cycles (two or four CCLK

cycles).

RCCLK — The internal 7.373 MHz RC oscillator output.

PCLK — Clock for the various peripheral devices and is CCLK

⁄

8.3.2 CPU clock (OSCCLK)

The P89LPC933/934/935/936 provides several user-selectable oscillator options in

generating the CPU clock. This allows optimization for a range of needs from high

precision to lowest possible cost. These options are conﬁgured when the ﬂash is

programmed and include an on-chip watchdog oscillator, an on-chip RC oscillator, an

oscillator using an external crystal, or an external clock source. The crystal oscillator can

be optimized for low, medium, or high frequency crystals covering a range from 20 kHz to

18 MHz.

8.3.3 Low speed oscillator option

This option supports an external crystal in the range of 20 kHz to 100 kHz. Ceramic

resonators are also supported in this conﬁguration.

8.3.4 Medium speed oscillator option

This option supports an external crystal in the range of 100 kHz to 4 MHz. Ceramic

resonators are also supported in this conﬁguration.

8.3.5 High speed oscillator option

This option supports an external crystal in the range of 4 MHz to 18 MHz. Ceramic

resonators are also supported in this conﬁguration.

8.3.6 Clock output

The P89LPC933/934/935/936 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,

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