18F8680 datasheet(157/496 Pages) MICROCHIP

157 / 496 page

 2004 Microchip Technology Inc.

DS30491C-page 155

PIC18F6585/8585/6680/8680

11.0

TIMER0 MODULE

The Timer0 module has the following features:

• Software selectable as an 8-bit or 16-bit timer/

counter

• Readable and writable

• Dedicated 8-bit software programmable prescaler

• Clock source selectable to be external or internal

• Interrupt-on-overflow from 0FFh to 00h in 8-bit

mode and 0FFFFh to 0000h in 16-bit mode

• Edge select for external clock

Figure 11-1 shows a simplified block diagram of the

Timer0 module in 8-bit mode and Figure 11-2 shows a

simplified block diagram of the Timer0 module in 16-bit

mode.

The T0CON register (Register 11-1) is a readable and

writable register that controls all the aspects of Timer0,

including the prescale selection.

T0CON: TIMER0 CONTROL REGISTER

Note:

Timer0 is enabled on POR.

R/W-1

TMR0ON

T08BIT

T0CS

T0SE

PSA

T0PS2

T0PS1

T0PS0

bit 7

bit 0

bit 7

TMR0ON: Timer0 On/Off Control bit

= Enables Timer0

= Stops Timer0

bit 6

T08BIT: Timer0 8-bit/16-bit Control bit

= Timer0 is configured as an 8-bit timer/counter

= Timer0 is configured as a 16-bit timer/counter

bit 5

T0CS: Timer0 Clock Source Select bit

= Transition on T0CKI pin

= Internal instruction cycle clock (CLKO)

bit 4

T0SE: Timer0 Source Edge Select bit

= Increment on high-to-low transition on T0CKI pin

= Increment on low-to-high transition on T0CKI pin

bit 3

PSA: Timer0 Prescaler Assignment bit

= TImer0 prescaler is not assigned. Timer0 clock input bypasses prescaler.

= Timer0 prescaler is assigned. Timer0 clock input comes from prescaler output.

bit 2-0

T0PS2:T0PS0: Timer0 Prescaler Select bits

111

= 1:256 prescale value

110

= 1:128 prescale value

101

= 1:64 prescale value

100

= 1:32 prescale value

011

= 1:16 prescale value

010

= 1:8

prescale value

001

= 1:4

prescale value

000

= 1:2

prescale value

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

- n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

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