P89LPC9381 NXP Semiconductors, P89LPC9381 Datasheet - Page 18

• Manufacturer Part Number: P89LPC9381
• Description: The P89LPC9381 is a single-chip microcontroller, available in low-cost packages, basedon a high performance processor architecture that executes instructions in two to fourclocks, six times the rate of standard 80C51 devices
• Manufacturer: NXP Semiconductors

Philips Semiconductors
P89LPC9381_1
Product data sheet
7.4 On-chip RC oscillator option
7.5 Watchdog oscillator option
7.6 External clock input option
The frequency of this clock output is
in Idle mode, it may be turned off prior to entering Idle, saving additional power.
The P89LPC9381 has a 6-bit TRIM register that can be used to tune the frequency of the
RC oscillator. During reset, the TRIM value is initialized to a factory pre-programmed
value to adjust the oscillator frequency to 7.373 MHz
End-user applications can write to the TRIM register to adjust the on-chip RC oscillator to
other frequencies.
The watchdog has a separate oscillator which has a frequency of 400 kHz. This oscillator
can be used to save power when a high clock frequency is not needed.
In this configuration, the processor clock is derived from an external source driving the
XTAL1/P3[1] pin. The rate may be from 0 Hz up to 18 MHz. The XTAL2/P3[0] pin may be
used as a standard port pin or a clock output. 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 V
specified level. When system power is removed V
specified operating voltage. When using an oscillator frequency above 12 MHz, in
some applications, an external brownout detect circuit may be required to hold the
device in reset when V
Fig 4. Block diagram of oscillator control
XTAL1
XTAL2
(400 kHz + 30 %
(7.3728 MHz
OSCILLATOR
OSCILLATOR
WATCHDOG
RC
MEDIUM FREQUENCY
HIGH FREQUENCY
LOW FREQUENCY
1 %)
20 %)
Rev. 01 — 8 September 2006
RCCLK
DD
falls below the minimum specified operating voltage.
1
TIMER 0 AND
2
TIMER 1
that of the CCLK. If the clock output is not needed
OSCCLK
DIVM
8-bit microcontroller with 10-bit ADC
I
2
DD
C-BUS
1 % at room temperature.
CCLK
PCLK
will fall below the minimum
PCLK
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
DD
2
P89LPC9381
has reached its
SPI
ADC0
WDT
RTC
CPU
UART
002aac463
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