P87LPC779FDH datasheet(34/74 Pages) PHILIPS

34 / 74 page

Philips Semiconductors

P87LPC779

CMOS single-chip 8-bit microcontroller

Product data

Rev. 02 — 03 May 2004

34 of 74

9397 750 13213

8.10 Oscillator

The P87LPC779 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.

8.10.1

Low speed oscillator option

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

8.10.2

Medium speed 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.

8.10.3

High speed oscillator option

This option supports an external crystal in the range of 4 MHz to 20 MHz. Ceramic

resonators are also supported in this conﬁguration.

Table 24:

KBI - Keyboard interrupt register (address 86H) bit description

Bit

Symbol

Description

When set, enables P0.7 as a cause of a Keyboard Interrupt.

When set, enables P0.6 as a cause of a Keyboard Interrupt.

When set, enables P0.5 as a cause of a Keyboard Interrupt.

When set, enables P0.4 as a cause of a Keyboard Interrupt.

When set, enables P0.3 as a cause of a Keyboard Interrupt.

When set, enables P0.2 as a cause of a Keyboard Interrupt.

When set, enables P0.1 as a cause of a Keyboard Interrupt.

When set, enables P0.0 as a cause of a Keyboard Interrupt.

Table 25:

Recommended oscillator capacitors for use with the low frequency oscillator option

Oscillator

Frequency

VDD = 2.7 V to 4.5 V

VDD = 4.5 V to 6.0 V

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

Table 26:

Recommended oscillator capacitors for use with the medium frequency oscillator option

Oscillator

Frequency

VDD = 2.7 V to 4.5 V

VDD = 4.5 V to 6.0 V

Lower Limit

Optimal Value

Upper Limit

Lower Limit

Optimal Value

Upper Limit

100 kHz

33 pF

47 pF

33 pF

47 pF

1 MHz

15 pF

33 pF

15 pF

22 pF

47 pF

4 MHz

15 pF

33 pF

15 pF

33 pF

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