p89lpc972fn NXP Semiconductors, p89lpc972fn Datasheet - Page 19

• Manufacturer Part Number: p89lpc972fn
• Description: 8-bit Microcontroller With Accelerated Two-clock 80c51 Core 2kb/4 Kb/8 Kb Wide-voltage Byte-erasable ?ash
• Manufacturer: NXP Semiconductors

NXP Semiconductors
P89LPC97X_1
Preliminary data sheet
7.3.1 Clock definitions
7.3.2 CPU clock (OSCCLK)
7.4.1 Low speed oscillator option
7.4.2 Medium speed oscillator option
7.4.3 High speed oscillator option
7.2 Enhanced CPU
7.3 Clocks
7.4 Crystal oscillator option
The P89LPC970/971/972 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.
The P89LPC970/971/972 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
Section 7.11 “CCLK modification: DIVM
Remark: 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. The clock doubler option, when
enabled, provides an output frequency of 14.746 MHz.
PCLK — Clock for the various peripheral devices and is
The P89LPC970/971/972 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 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.
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 18 MHz. Ceramic
resonators are also supported in this configuration.
osc
Figure
is defined as the OSCCLK frequency.
5) and can also be optionally divided to a slower frequency (see
Rev. 01 — 17 December 2009
8-bit microcontroller with accelerated two-clock 80C51 core
register”).
P89LPC970/971/972
CCLK
2
.
© NXP B.V. 2009. All rights reserved.
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