PIC16F917ESLASHML301 datasheet(77/272 Pages) MICROCHIP

77 / 272 page

Preliminary

DS41250E-page 75

PIC16F917/916/914/913

4.3.4

EXTERNAL RC MODES

The External Resistor-Capacitor (RC) modes support

the use of an external RC circuit. This allows the

designer maximum flexibility in frequency choice while

keeping costs to a minimum when clock accuracy is not

required. There are two modes, RC and RCIO.

In RC mode, the RC circuit connects to the OSC1 pin.

The OSC2/CLKO pin outputs the RC oscillator

frequency divided by 4. This signal may be used to

provide a clock for external circuitry, synchronization,

calibration, test or other application requirements.

Figure 4-5 shows the RC mode connections.

FIGURE 4-5:

RC MODE

In RCIO mode, the RC circuit is connected to the OSC1

pin. The OSC2 pin becomes an additional general

purpose I/O pin. The I/O pin becomes bit 4 of PORTA

(RA4). Figure 4-6 shows the RCIO mode connections.

FIGURE 4-6:

RCIO MODE

The RC oscillator frequency is a function of the supply

voltage, the resistor (REXT) and capacitor (CEXT)

values and the operating temperature. In addition to

this, the oscillator frequency will vary from unit to unit

due to normal threshold voltage. Furthermore, the

difference in lead frame capacitance between package

types will also affect the oscillation frequency or for low

CEXT values. The user also needs to take into account

variation due to tolerance of external RC components

used.

4.4

Internal Clock Modes

The PIC16F917/916/914/913 has two independent,

internal oscillators that can be configured or selected

as the system clock source.

The

HFINTOSC

(High-Frequency

Internal

Oscillator) is factory calibrated and operates at

8 MHz. The frequency of the HFINTOSC can be

user adjusted ±12% via software using the

OSCTUNE register (Register 4-2).

The

LFINTOSC

(Low-Frequency

Internal

Oscillator) is uncalibrated and operates at

approximately 31 kHz.

The system clock speed can be selected via software

using the Internal Oscillator Frequency Select (IRCF)

bits.

The system clock can be selected between external or

internal clock sources via the System Clock Selection

(SCS) bit (see Section 4.5 “Clock Switching”).

4.4.1

INTOSC AND INTOSCIO MODES

The INTOSC and INTOSCIO modes configure the

internal oscillators as the system clock source when the

device is programmed using the Oscillator Selection

(FOSC)

bits

in the Configuration Word register

(Register 16-1).

In INTOSC mode, the OSC1 pin is available for general

purpose I/O. The OSC2/CLKO pin outputs the selected

internal oscillator frequency divided by 4. The CLKO

signal may be used to provide a clock for external

circuitry, synchronization, calibration, test or other

application requirements.

In INTOSCIO mode, the OSC1 and OSC2 pins are

available for general purpose I/O.

4.4.2

HFINTOSC

The High-Frequency Internal Oscillator (HFINTOSC) is

a factory calibrated 8 MHz internal clock source. The

frequency

the

HFINTOSC

can

altered

approximately ±12% via software using the OSCTUNE

The output of the HFINTOSC connects to a postscaler

and multiplexer (see Figure 4-1). One of seven

frequencies can be selected via software using the

IRCF bits (see Section 4.4.4 “Frequency Select Bits

(IRCF)”).

The HFINTOSC is enabled by selecting any frequency

between 8 MHz and 125 kHz (IRCF

≠ 000) as the

System Clock Source (SCS = 1), or when Two-Speed

Start-up is enabled (IESO = 1 and IRCF

≠ 000).

The HF Internal Oscillator (HTS) bit (OSCCON<2>)

indicates whether the HFINTOSC is stable or not.

OSC2/CLKO

CEXT

REXT

PIC16F917/916/914/913

OSC1

FOSC/4

Internal

Clock

VDD

VSS

Recommended values: 3 k

Ω ≤ REXT ≤ 100 kΩ

CEXT > 20 pF

I/O (OSC2)

CEXT

REXT

PIC16F917/916/914/913

OSC1

RA6

Internal

Clock

VDD

VSS

Recommended values:3 k

Ω ≤ REXT ≤ 100 kΩ

CEXT > 20 pF

PIC16F917E/ML301 Datasheet(PDF) 77 Page - Microchip Technology

PIC16F917E/ML301 Datasheet(HTML) 77 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL