PIC16F1933-ESLASHP datasheet(111/418 Pages) MICROCHIP

111 / 418 page

Preliminary

DS41364A-page 109

PIC16F193X/LF193X

8.3

Clock Source Modes

Clock Source modes can be classified as external or

internal.

• External Clock modes rely on external circuitry for

the clock source. Examples are: oscillator mod-

ules (EC mode), quartz crystal resonators or

ceramic resonators (LP, XT and HS modes) and

Resistor-Capacitor (RC) mode circuits.

• Internal clock sources are contained internally

within the oscillator module. The oscillator module

has two internal oscillators: the 16 MHz

High-Frequency Internal Oscillator (HFINTOSC),

500 kHZ (MFINTOSC) and the 31 kHz

Low-Frequency Internal Oscillator (LFINTOSC).

The system clock can be selected between external or

internal clock sources via the System Clock Select

(SCS) bit of the OSCCON register. See Section 8.6

“Clock Switching” for additional information. When

switching between clock sources, a delay is required to

allow the new clock to stabilize. These oscillator delays

are shown in Table 8-1.

8.4

External Clock Modes

8.4.1

OSCILLATOR START-UP TIMER (OST)

If the oscillator module is configured for LP, XT or HS

modes, the Oscillator Start-up Timer (OST) counts

1024 oscillations from OSC1. This occurs following a

Power-on Reset (POR) and when the Power-up Timer

(PWRT) has expired (if configured), or a wake-up from

Sleep. During this time, the program counter does not

increment and program execution is suspended. The

OST ensures that the oscillator circuit, using a quartz

crystal resonator or ceramic resonator, has started and

is providing a stable system clock to the oscillator

module.

In order to minimize latency between external oscillator

start-up and code execution, the Two-Speed Clock

Start-up mode can be selected (see Section 8.6.3

“Timer1 Oscillator Ready (T1OSCR) Bit”).

TABLE 8-1:

OSCILLATOR SWITCHING DELAYS

8.4.2

EC MODE

The External Clock (EC) mode allows an externally

generated logic level as the system clock source. When

operating in this mode, an external clock source is

connected to the OSC1 input. OSC2/CLKOUT is

available for general purpose I/O or CLKOUT.

Figure 8-2 shows the pin connections for EC mode.

The Oscillator Start-up Timer (OST) is disabled when

EC mode is selected. Therefore, there is no delay in

operation after a Power-on Reset (POR) or wake-up

from Sleep. Because the PIC® MCU design is fully

static, stopping the external clock input will have the

effect of halting the device while leaving all data intact.

Upon restarting the external clock, the device will

resume operation as if no time had elapsed.

FIGURE 8-2:

EXTERNAL CLOCK (EC)

MODE OPERATION

Switch From

Switch To

Frequency

Oscillator Delay

Sleep/POR

LFINTOSC(1)

MFINTOSC(1)

HFINTOSC(1)

31 kHz

31.25 kHz-500 kHz

31.25kHz-16MHz

Oscillator Warm-up Delay (TWARM)

Sleep/POR

EC, RC(1)

DC – 32 MHz

2 cycles

LFINTOSC

EC, RC(1)

DC – 32 MHz

1 cycle of each

Sleep/POR

Timer1 Oscillator

LP, XT, HS(1)

32 kHz-20 MHz

1024 Clock Cycles (OST)

Any clock source

MFINTOSC(1)

HFINTOSC(1)

31.25 kHz-500 kHz

31.25kHz-16MHz

μs (approx.)

Any clock source

LFINTOSC(1)

31 kHz

1 cycle of each

Any clock source

Timer1 Oscillator

32 kHz

1024 Clock Cycles (OST)

PLL inactive

PLL active

16-32 MHz

2 ms (approx.)

Note 1:

PLL inactive.

OSC1/CLKIN

OSC2/CLKOUT(1)

Clock from

Ext. System

PIC® MCU

FOSC/4 or

I/O(1)

Note

Output depends upon CLKOUTEN bit of the

Configuration Word 1.

PIC16F1933-E/P Datasheet(PDF) 111 Page - Microchip Technology

PIC16F1933-E/P Datasheet(HTML) 111 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