PIC12F519T-ESLASHMS datasheet(41/88 Pages) MICROCHIP

41 / 88 page

Preliminary

DS41319A-page 39

PIC12F519

8.2.5

INTERNAL 4/8 MHz RC

OSCILLATOR

The internal RC oscillator provides a fixed 4/8 MHz

(nominal) system clock at VDD = 5V and 25°C, (see

Section 11.0

“Electrical

Characteristics”

for

information on variation over voltage and temperature).

In addition, a calibration instruction is programmed into

the last address of memory, which contains the calibra-

tion value for the internal RC oscillator. This location is

always non-code protected, regardless of the

code-protect settings. This value is programmed as a

MOVLW XX instruction where XX is the calibration value,

and is placed at the Reset vector. This will load the W

PC will then roll over to the users program at address

0x000. The user then has the option of writing the value

to the OSCCAL Register (05h) or ignoring it.

OSCCAL, when written to with the calibration value, will

“trim” the internal oscillator to remove process variation

from the oscillator frequency.

For the PIC12F519 device, only bits <7:1> of OSCCAL

are used for calibration. See Register 4-3 for more

information.

8.3

Reset

The device differentiates between various kinds of

Reset:

• Power-on Reset (POR)

•MCLR Reset during normal operation

•MCLR Reset during Sleep

• WDT Time-out Reset during normal operation

• WDT Time-out Reset during Sleep

• Wake-up from Sleep on pin change

Some registers are not reset in any way, and they are

unknown on Power-on Reset (POR) and unchanged in

any other Reset. Most other registers are reset to

“Reset state” on Power-on Reset (POR), MCLR, WDT

or Wake-up on pin change Reset during normal opera-

tion. They are not affected by a WDT Reset during

Sleep or MCLR Reset during Sleep, since these

Resets are viewed as resumption of normal operation.

The exceptions to this are TO, PD and RBWUF bits.

They are set or cleared differently in different Reset sit-

uations. These bits are used in software to determine

the nature of Reset. See Table 8-3 for a full description

of Reset states of all registers.

Note:

Erasing the device will also erase the

pre-programmed internal calibration value

for the internal oscillator. The calibration

value must be read prior to erasing the

part so it can be reprogrammed correctly

later.

Note:

The bit 0 of the OSCCAL register is

unimplemented and should be written as

‘0’

when

modifying

OSCCAL

for

compatibility with future devices.

PIC12F519T-E/MS Datasheet(PDF) 41 Page - Microchip Technology

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