P89LPC913 datasheet(26/63 Pages) PHILIPS

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Philips Semiconductors

P89LPC912/913/914

8-bit microcontrollers with two-clock 80C51 core

Product data

Rev. 03 — 17 December 2004

26 of 63

9397 750 14468

Functional description

Remark: Please refer to the

P89LPC912/913/914 User’s Manual for a more detailed

functional description.

9.1 Enhanced CPU

The P89LPC912/913/914 uses an enhanced 80C51 CPU which runs at 6 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.

9.2 Clocks

9.2.1

Clock deﬁnitions

The P89LPC912/913/914 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 10, 11, and 12) and can also be optionally divided to a

slower frequency (see Section 9.7 “CPU Clock (CCLK) modiﬁcation: DIVM register”).

Note: 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/2

9.2.2

CPU clock (OSCCLK)

The P89LPC912/913/914 provide 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 and an on-chip RC oscillator.

In addition, both the P89LPC912 and P89LPC913 provide 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 12 MHz.

9.2.3

Low speed oscillator option (P89LPC912, P89LPC913)

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

resonators are also supported in this conﬁguration.

9.2.4

Medium speed oscillator option (P89LPC912, P89LPC913)

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

resonators are also supported in this conﬁguration.

9.2.5

High speed oscillator option (P89LPC912, P89LPC913)

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

resonators are also supported in this conﬁguration. When using an oscillator

frequency above 12 MHz, the reset input function of P1.5 must be enabled. An

external circuit is required to hold the device in reset at power-up until VDD has

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