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PIC16LC505T-20E/SL

14-Pin, 8-Bit CMOS Microcontroller

Microchip Technology 

PIC16C505

7.0 SPECIAL FEATURES OF THE

CPU

What sets a microcontroller apart from other

processors are special circuits to deal with the needs

of real-time applications. The PIC16C505

microcontroller has a host of such features intended to

maximize system reliability, minimize cost through

elimination of external components, provide power

saving operating modes and offer code protection.

These features are:

• Oscillator selection

• Reset

- Power-On Reset (POR)

- Device Reset Timer (DRT)

- Wake-up from SLEEP on pin change

• Watchdog Timer (WDT)

• SLEEP

• Code protection

• ID locations

• In-circuit Serial Programming

• Clock Out

The PIC16C505 has a Watchdog Timer, which can be

shut off only through configuration bit WDTE. It runs

off of its own RC oscillator for added reliability. If using

HS, XT or LP selectable oscillator options, there is

always an 18 ms (nominal) delay provided by the

Device Reset Timer (DRT), intended to keep the chip

in reset until the crystal oscillator is stable. If using

INTRC or EXTRC, there is an 18 ms delay only on VDD

power-up. With this timer on-chip, most applications

need no external reset circuitry.

The SLEEP mode is designed to offer a very low

current power-down mode. The user can wake-up

from SLEEP through a change on input pins or

through a Watchdog Timer time-out. Several oscillator

options are also made available to allow the part to fit

the application, including an internal 4 MHz oscillator.

The EXTRC oscillator option saves system cost while

the LP crystal option saves power. A set of

configuration bits are used to select various options.

7.1 Configuration Bits

The PIC16C505 configuration word consists of 12 bits.

Configuration bits can be programmed to select

various device configurations. Three bits are for the

selection of the oscillator type, one bit is the Watchdog

Timer enable bit, and one bit is the MCLR enable bit.

Seven bits are for code protection (Register 7-1).

REGISTER 7-1: CONFIGURATION WORD FOR PIC16C505

CP CP CP CP CP CP MCLRE CP WDTE FOSC2 FOSC1 FOSC0

bit11

10

9

8

7

6

5

4

3

2

1

bit0

bit 11-6, 4: CP Code Protection bits (1)(2)(3)

bit 5:

MCLRE: RB3/MCLR pin function select

1 = RB3/MCLR pin function is MCLR

0 = RB3/MCLR pin function is digital I/O, MCLR internally tied to VDD

bit 3:

WDTE: Watchdog timer enable bit

1 = WDT enabled

0 = WDT disabled

bit 2-0:

Note 1:

2:

3:

FOSC<1:0>: Oscillator Selection bits

111 = external RC oscillator/CLKOUT function on RB4/OSC2/CLKOUT pin

110 = external RC oscillator/RB4 function on RB4/OSC2/CLKOUT pin

101 = internal RC oscillator/CLKOUT function on RB4/OSC2/CLKOUT pin

100 = internal RC oscillator/RB4 function on RB4/OSC2/CLKOUT pin

011 = invalid selection

010 = HS oscillator

001 = XT oscillator

000 = LP oscillator

03FFh is always uncode protected on the PIC16C505. This location contains the

MOVLWxx calibration instruction for the INTRC.

Refer to the PIC16C505 Programming Specifications to determine how to access the con-

figuration word. This register is not user addressable during device operation.

All code protect bits must be written to the same value.

Register: CONFIG

Address(2): 0FFFh

© 1999 Microchip Technology Inc.

DS40192C-page 27

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