p87lpc778 NXP Semiconductors, p87lpc778 Datasheet - Page 40

• Manufacturer Part Number: p87lpc778
• Description: Cmos Single-chip 8-bit 80c51 Microcontroller 128-byte Data Ram, 8 Kb Otp
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Table 39:
9397 750 12378
Product data
Oscillator
Frequency
4 MHz
8 MHz
16 MHz
20 MHz
Recommended oscillator capacitors for use with the high frequency oscillator option
V
Lower Limit
15 pF
15 pF
-
-
DD
8.10.4 On-chip RC oscillator option
8.10.5 External clock input option
8.10.6 Clock output
= 2.7 V to 4.5 V
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. A clock output on the
X2 / P2.0 pin may be enabled when the on-chip RC oscillator is used.
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 V
up to 10 MHz when V
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.
The P87LPC778 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 P87LPC778. 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
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.
Fig 14. Using the crystal oscillator.
Optimal Value
33 pF
15 pF
-
-
The oscillator must be configured in one of the following modes: Low frequency crystal,
medium frequency crystal, or high frequency crystal.
(1) A series resistor may be required to limit crystal drive levels. This is especially important
for low frequency crystals (see text).
Rev. 01 — 31 March 2004
Upper Limit
47 pF
33 pF
-
-
DD
is below 4.5 V. When the external clock input mode is used,
ceramic resonator
quartz crystal or
V
Lower Limit
15 pF
15 pF
15 pF
15 pF
DD
= 4.5 V to 5.5 V
CMOS single-chip 8-bit microcontroller
[1]
X1
X2
87LPC77x
002aaa632
Optimal Value
33 pF
33 pF
15 pF
15 pF
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
P87LPC778
DD
is above 4.5 V and
Upper Limit
68 pF
47 pF
33 pF
33 pF
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