P89LPC983FDH datasheet(33/85 Pages) NXP

33 / 85 page

P89LPC980_982_983_985_2

Preliminary data sheet

Rev. 02 — 8 February 2010

33 of 85

NXP Semiconductors

P89LPC980/982/983/985

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

7.2 Enhanced CPU

The P89LPC980/982/983/985 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 P89LPC980/982/983/985 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 9) 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 P89LPC980/982/983/985 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 Crystal oscillator option

The crystal oscillator option 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.

P89LPC983FDH Datasheet(PDF) 33 Page - NXP Semiconductors

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