P89LPC9321 datasheet(21/70 Pages) NXP

21 / 70 page

P89LPC9321_1

Product data sheet

Rev. 01 — 9 December 2008

21 of 70

NXP Semiconductors

P89LPC9321

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

7.2 Enhanced CPU

The P89LPC9321 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.

7.3 Clocks

7.3.1 Clock deﬁnitions

The P89LPC9321 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 6) and can also be optionally divided to a slower frequency (see

Section 7.11 “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. The clock doubler option, when

enabled, provides an output frequency of 14.746 MHz.

PCLK — Clock for the various peripheral devices and is CCLK

⁄

7.3.2 CPU clock (OSCCLK)

The P89LPC9321 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.

7.4 External crystal oscillator option

The external crystal oscillator can be optimized for low, medium, or high frequency

crystals covering a range from 20 kHz to 18 MHz. It can be the clock source of OSCCLK,

RTC and WDT.

7.4.1 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.

7.4.2 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.

7.4.3 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.

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