PIC16C505T-04/SL Ver la hoja de datos (PDF) - Microchip Technology

Número de pieza

componentes Descripción

Fabricante

PIC16C505T-04/SL

14-Pin, 8-Bit CMOS Microcontroller

Microchip Technology 

PIC16C505

7.2.5 INTERNAL 4 MHz RC OSCILLATOR

The internal RC oscillator provides a fixed 4 MHz (nom-

inal) system clock at VDD = 5V and 25°C, see Electrical

Specifications section 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 protected, regardless of the code protect set-

tings. 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 register

with the calibration value upon reset and the 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.

Note:

Please note that 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 repro-

grammed correctly later.

For the PIC16C505, only bits <7:2> of OSCCAL are

implemented.

7.3 RESET

The device differentiates between various kinds of

reset:

a) Power on reset (POR)

b) MCLR reset during normal operation

c) MCLR reset during SLEEP

d) WDT time-out reset during normal operation

e) WDT time-out reset during SLEEP

f) Wake-up from SLEEP on pin change

Some registers are not reset in any way, they are

unknown on 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 operation. 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 situations. These bits are

used in software to determine the nature of reset. See

Table 7-3 for a full description of reset states of all

registers.

DS40192C-page 30

© 1999 Microchip Technology Inc.

Share Link: