P89LPC920FDH PHILIPS [NXP Semiconductors], P89LPC920FDH Datasheet - Page 14

• Manufacturer Part Number: P89LPC920FDH
• Description: 8-bit microcontrollers with two-clock 80C51 core 2 kB/4 kB/8 kB 3 V low-power Flash with 256-byte data RAM
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
8. Functional description
9397 750 12285
Product data
8.2.1 Clock definitions
8.2.2 CPU clock (OSCCLK)
8.2.3 Low speed oscillator option
8.2.4 Medium speed oscillator option
8.2.5 High speed oscillator option
8.1 Enhanced CPU
8.2 Clocks
Remark: Please refer to the P89LPC920/921/922 User’s Manual for a more detailed
functional description.
The P89LPC920/921/922 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.
The P89LPC920/921/922 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
(see
Note: f
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
The P89LPC920/921/922 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 12 MHz.
This option supports an external crystal in the range of 20 kHz to 100 kHz. Ceramic
resonators are also supported in this configuration.
This option supports an external crystal in the range of 100 kHz to 4 MHz. Ceramic
resonators are also supported in this configuration.
This option supports an external crystal in the range of 4 MHz to 12 MHz. Ceramic
resonators are also supported in this configuration.
Section 8.7 “CPU Clock (CCLK) modification: DIVM
OSC
is defined as the OSCCLK frequency.
Rev. 06 — 21 November 2003
Figure
5) and can also be optionally divided to a slower frequency
8-bit microcontrollers with two-clock 80C51 core
P89LPC920/921/922
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
register”).
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