PIC18F010T-ISLASHP datasheet(15/176 Pages) MICROCHIP

15 / 176 page

 2001 Microchip Technology Inc.

Preliminary

DS41142A-page 13

PIC18F010/020

2.8

Power-up Delays

Power-up delays are controlled by two timers, so that

no external RESET circuitry is required for most appli-

cations. The delays ensure that the device is kept in

RESET until the device power supply and clock are sta-

ble. For additional information on RESET operation,

see the “RESET” section.

The first timer is the Power-up Timer (PWRT), which

optionally provides a fixed delay of 72 ms (nominal) on

power-up only (POR and BOR). The second timer is

the Oscillator Start-up Timer OST, intended to keep the

chip in RESET until the crystal oscillator is stable.

2.9

Frequency Calibrations

The 8 MHz frequency is calibrated at the factory. Since

the 4 MHz and 1 MHz clock outputs are derived digitally

from the 8 MHz, the accuracy specifications of the 4

MHz and 1 MHz clocks are the same as the 8 MHz.

The 500 kHz and 32 kHz frequencies are not cali-

brated. The 500 kHz and 32 kHz are nominal frequen-

cies. Their accuracy specifications are shown in the

Specifications section.

2.10

Frequency Tuning in User Mode

In addition to the factory calibration, 8 MHz frequency

can be tuned in the user’s application. This frequency

tuning capability allows user to deviate from the factory

calibrated frequency. The user can tune the frequency

by writing to the OSCTUNE register. See Register 2-2

for details of the OSCTUNE register. The tuning range

of the 8 MHz oscillator is ±1 MHz, or ±12.5% nominal.

See the Specifications section for further specification

details.

Since the 4 MHz and 1 MHz are derived from the 8

MHz, the tuning range of the 4 MHz is ±500 kHz nomi-

nal, and the tuning range of the 1 MHz is ±125 kHz

nominal. The tuning sensitivity (%FINTOSC/bit) is con-

stant throughout the frequency selections and tuning

range.

OSCTUNE REGISTER (ADDRESS 0F9Bh)

Note:

Frequency tuning is not available in the

500 kHz and 32 kHz frequencies.

U-0

R/W-0

—

TUN5

TUN4

TUN3

TUN2

TUN1

TUN0

bit 7

bit 0

bit 7-6

Unimplemented: Read as ‘0’

bit 5-0

TUN<5:0>: 6-bit Frequency Tuning

011111

= Maximum frequency

011110

•

000001

000000

= Center frequency. Oscillator module is running at the calibrated frequency.

111111

•

100000

= Minimum frequency

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

- n = Value at POR

’1’ = Bit is set

’0’ = Bit is cleared

x = Bit is unknown

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