P12C508 datasheet(32/84 Pages) MICROCHIP

32 / 84 page

PIC12C5XX

DS40139A-page 32

Advanced Information

7.5

Device Reset Timer (DRT)

In the PIC12C5XX, the DRT runs any time the device

is powered up. DRT runs from RESET only in XT and

LP modes. It is disabled from RESET in INTRC and

EXTRC modes.

The Device Reset Timer (DRT) provides a ﬁxed 18 ms

nominal time-out on reset. The DRT operates on an

internal RC oscillator. The processor is kept in RESET

as long as the DRT is active. The DRT delay allows

VDD to rise above VDD min., and for the oscillator to

stabilize.

Oscillator circuits based on crystals or ceramic

resonators require a certain time after power-up to

establish a stable oscillation. The on-chip DRT keeps

the device in a RESET condition for approximately 18

ms after the voltage on the GP3/MCLR/VPP pin has

reached a logic high (VIHMC) level. Thus, external RC

networks connected to the MCLR input are not

required in most cases, allowing for savings in cost-

sensitive and/or space restricted applications.

The Device Reset time delay will vary from chip to chip

due to VDD, temperature, and process variation. See

AC parameters for details.

The DRT will also be triggered upon a Watchdog

Timer time-out (only in XT and LP modes). This is

particularly important for applications using the WDT

to wake from SLEEP mode automatically.

7.6

Watchdog Timer (WDT)

The Watchdog Timer (WDT) is a free running on-chip

RC oscillator which does not require any external

components. This RC oscillator is separate from the

external RC oscillator of the GP5/OSC1/CLKIN pin

and the internal 4 MHz oscillator. That means that the

WDT will run even if the clock on the GP5/OSC1/

CLKIN and GP4/OSC2 pins have been stopped, for

example, by execution of a SLEEP instruction. During

normal operation or SLEEP, a WDT reset or wake-up

reset generates a device RESET.

The TO bit (STATUS<4>) will be cleared upon a

Watchdog Timer reset.

The

WDT

can

permanently

disabled

programming the conﬁguration bit WDTE as a '0'

(Section 7.1). Refer to the PIC12C5XX Programming

Speciﬁcations to determine how to access the

conﬁguration word.

P12C508 Arkusz danych(PDF) 32 Page - Microchip Technology

P12C508 Arkusz danych(HTML) 32 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

Arkusz danych Pobierz

Link URL