P89LPC934 PHILIPS [NXP Semiconductors], P89LPC934 Datasheet - Page 25

• Manufacturer Part Number: P89LPC934
• Description: 8-bit microcontroller with accelerated two-clock 80C51 core 4 kB/8 kB 3 V byte-erasable Flash with 8-bit A/D converters
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
9397 750 15113
Product data sheet
8.4 On-chip RC oscillator option
8.5 Watchdog oscillator option
8.6 External clock input option
external clock input on X1) and if the RTC is not using the crystal oscillator as its clock
source. This allows external devices to synchronize to the P89LPC933/934/935/936. This
output is enabled by the ENCLK bit in the TRIM register.
The frequency of this clock output is
in Idle mode, it may be turned off prior to entering Idle, saving additional power.
The P89LPC933/934/935/936 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
preprogrammed value to adjust the oscillator frequency to 7.373 MHz
temperature. 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
Rev. 06 — 20 June 2005
DD
8-bit microcontroller with accelerated two-clock 80C51 core
falls below the minimum specified operating voltage.
1
2
P89LPC933/934/935/936
that of the CCLK. If the clock output is not needed
DD
will fall below the minimum
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
DD
has reached its
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