P87LPC767FD datasheet(28/60 Pages) PHILIPS

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Philips Semiconductors

Product data

87LPC767

Low power, low price, low pin count (20 pin)

microcontroller with 4-kbyte OTP and 8-bit A/D converter

2001 Aug 07

Oscillator

The 87LPC767 provides several user selectable oscillator options,

allowing optimization for a range of needs from high precision to

lowest possible cost. These are configured when the EPROM is

programmed. Basic oscillator types that are supported include: low,

medium, and high speed crystals, covering a range from 20 kHz to

20 MHz; ceramic resonators; and on-chip RC oscillator.

Low Frequency Oscillator Option

This option supports an external crystal in the range of 20 kHz to 100 kHz.

Table 5 shows capacitor values that may be used with a quartz crystal in this mode.

Table 5. Recommended oscillator capacitors for use with the low frequency oscillator option

Oscillator

VDD = 2.7 to 4.5 V

VDD = 4.5 to 6.0 V

Frequency

Lower Limit

Optimal Value

Upper Limit

Lower Limit

Optimal Value

Upper Limit

20 kHz

15 pF

33 pF

47 pF

32 kHz

15 pF

33 pF

47 pF

100 kHz

15 pF

33 pF

15 pF

33 pF

Medium Frequency Oscillator Option

This option supports an external crystal in the range of 100 kHz to 4 MHz. Ceramic resonators are also supported in this configuration.

Table 6 shows capacitor values that may be used with a quartz crystal in this mode.

Table 6. Recommended oscillator capacitors for use with the medium frequency oscillator option

Oscillator Freq ency

VDD = 2.7 to 4.5 V

Oscillator Frequency

Lower Limit

Optimal Value

Upper Limit

100 kHz

33 pF

47 pF

1 MHz

15 pF

33 pF

4 MHz

15 pF

33 pF

High Frequency Oscillator Option

This option supports an external crystal in the range of 4 to 20 MHz. Ceramic resonators are also supported in this configuration.

Table 7 shows capacitor values that may be used with a quartz crystal in this mode.

Table 7. Recommended oscillator capacitors for use with the high frequency oscillator option

Oscillator

VDD = 2.7 to 4.5 V

VDD = 4.5 to 6.0 V

Frequency

Lower Limit

Optimal Value

Upper Limit

Lower Limit

Optimal Value

Upper Limit

4 MHz

15 pF

33 pF

47 pF

15 pF

33 pF

68 pF

8 MHz

15 pF

33 pF

15 pF

33 pF

47 pF

16 MHz

–

15 pF

33 pF

20 MHz

–

15 pF

33 pF

On-Chip RC Oscillator Option

The on-chip RC oscillator option has a typical frequency of 6 MHz

and can be divided down for slower operation through the use of the

DIVM register. Note that the on-chip oscillator has a

±25% frequency

tolerance and for that reason may not be suitable for use in some

applications. A clock output on the X2/P2.0 pin may be enabled

when the on-chip RC oscillator is used.

External Clock Input Option

In this configuration, the processor clock is input from an external

source driving the X1/P2.1 pin. The rate may be from 0 Hz up to

20 MHz when VDD is above 4.5 V and up to 10 MHz when VDD is

below 4.5 V. When the external clock input mode is used, the X2/P2.0

pin may be used as a standard port pin. A clock output on the X2/P2.0

pin may be enabled when the external clock input is used.

Clock Output

The 87LPC767 supports a clock output function when either the

on-chip RC oscillator or external clock input options are selected.

This allows external devices to synchronize to the 87LPC767. When

enabled, via the ENCLK bit in the P2M1 register, the clock output

appears on the X2/CLKOUT pin whenever the on-chip oscillator is

running, including in Idle mode. The frequency of the clock output is

1/6 of the CPU clock rate. If the clock output is not needed in Idle

mode, it may be turned off prior to entering Idle, saving additional

power. The clock output may also be enabled when the external

clock input option is selected.

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P87LPC767FD 数据表(PDF) 28 Page - NXP Semiconductors

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