P89LPC901 PHILIPS [NXP Semiconductors], P89LPC901 Datasheet - Page 24

• Manufacturer Part Number: P89LPC901
• Description: 8-bit microcontrollers with two-clock 80C51 core 1 kB 3 V Flash with 128-byte RAM
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
8. Functional description
9397 750 12293
Product data
8.2.1 Clock definitions
8.2.2 CPU clock (OSCCLK)
8.2.3 Low speed oscillator option (P89LPC901)
8.2.4 Medium speed oscillator option (P89LPC901)
8.1 Enhanced CPU
8.2 Clocks
Remark: Please refer to the P89LPC901/902/903 User’s Manual for a more detailed
functional description.
The P89LPC901/902/903 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 P89LPC901/902/903 device has several internal clocks as defined below:
OSCCLK — Input to the DIVM clock divider. OSCCLK is selected from one of the
clock sources (see Figures 12, 13, and 14) and can also be optionally divided to a
slower frequency (see
register”).
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 P89LPC901/902/903 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 and an on-chip RC
oscillator.
The P89LPC901, in addition, includes an option for 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.
OSC
is defined as the OSCCLK frequency.
Rev. 04 — 21 November 2003
Section 8.7 “CPU CLOCK (CCLK) modification: DIVM
8-bit microcontrollers with two-clock 80C51 core
P89LPC901/902/903
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
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