PIC16F636T-I/SL(2005) View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC16F636T-I/SL
(Rev.:2005)

8/14-Pin Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology

Microchip Technology 

PIC12F635/PIC16F636/639

5.3 Using Timer0 with an External

Clock

When no prescaler is used, the external clock input is the

same as the prescaler output. The synchronization of

T0CKI, with the internal phase clocks, is accomplished

by sampling the prescaler output on the Q2 and Q4

cycles of the internal phase clocks. Therefore, it is

necessary for T0CKI to be high for at least 2 TOSC (and a

small RC delay of 20 ns) and low for at least 2 TOSC (and

a small RC delay of 20 ns). Refer to the electrical

specification of the desired device.

Note:

The CMCON0 (19h) register must be ini-

tialized to configure an analog channel as

a digital input. Pins configured as analog

inputs will read ‘0’.

REGISTER 5-1:

OPTION_REG – OPTION REGISTER (ADDRESS: 81h)

R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1

RAPU INTEDG T0CS

T0SE

PSA

PS2

bit 7

R/W-1

PS1

R/W-1

PS0

bit 0

bit 7

bit 6

bit 5

bit 4

bit 3

bit 2-0

RAPU: PORTA Pull-up Enable bit

1 = PORTA pull-ups are disabled

0 = PORTA pull-ups are enabled by individual values in the WPUDA register

INTEDG: Interrupt Edge Select bit

1 = Interrupt on rising edge of RA2/T0CKI/INT/C1OUT pin

0 = Interrupt on falling edge of RA2/T0CKI/INT/C1OUT pin

T0CS: TMR0 Clock Source Select bit

1 = Transition on RA2/T0CKI/INT/C1OUT pin

0 = Internal instruction cycle clock (CLKOUT)

T0SE: TMR0 Source Edge Select bit

1 = Increment on high-to-low transition on RA2/T0CKI/INT/C1OUT pin

0 = Increment on low-to-high transition on RA2/T0CKI/INT/C1OUT pin

PSA: Prescaler Assignment bit

1 = Prescaler is assigned to the WDT

0 = Prescaler is assigned to the Timer0 module

PS<2:0>: Prescaler Rate Select bits

Bit Value TMR0 Rate WDT Rate(1)

000

1:2

1:1

001

1:4

1:2

010

1:8

1:4

011

1 : 16

1:8

100

1 : 32

1 : 16

101

1 : 64

1 : 32

110

1 : 128 1 : 64

111

1 : 256 1 : 128

Note 1: A dedicated 16-bit WDT postscaler is available for the PIC12F635/PIC16F636/639.

See Section 12.11 “Watchdog Timer (WDT)” for more information.

Legend:

R = Readable bit

- n = Value at POR

W = Writable bit

‘1’ = Bit is set

U = Unimplemented bit, read as ‘0’

‘0’ = Bit is cleared x = Bit is unknown

DS41232B-page 54

Preliminary

© 2005 Microchip Technology Inc.

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