PIC10F206-E/P(2014) 查看數據表（PDF） - Microchip Technology

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PIC10F206-E/P
(Rev.:2014)

6-Pin, 8-Bit Flash Microcontrollers

Microchip Technology 

PIC10F200/202/204/206

7.1.2 TIMER0 INCREMENT DELAY

Since the prescaler output is synchronized with the

internal clocks, there is a small delay from the time the

external clock edge occurs to the time the Timer0

module is actually incremented. Figure 7-4 shows the

delay from the external clock edge to the timer

incrementing.

FIGURE 7-4:

TIMER0 TIMING WITH EXTERNAL CLOCK

External Clock Input or

Prescaler Output(2)

External Clock/Prescaler

Output After Sampling

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

Small pulse

misses sampling

(1)

(3)

Increment Timer0 (Q4)

Timer0

T0

T0 + 1

T0 + 2

Note 1: Delay from clock input change to Timer0 increment is 3 TOSC to 7 TOSC (Duration of Q = TOSC). Therefore, the error

in measuring the interval between two edges on Timer0 input = ±4 TOSC max.

2: External clock if no prescaler selected; prescaler output otherwise.

3: The arrows indicate the points in time where sampling occurs.

7.2 Prescaler

An 8-bit counter is available as a prescaler for the

Timer0 module or as a postscaler for the Watchdog

Timer (WDT), respectively (see Figure 9-6). For

simplicity, this counter is being referred to as

“prescaler” throughout this data sheet.

Note:

The prescaler may be used by either the

Timer0 module or the WDT, but not both.

Thus, a prescaler assignment for the

Timer0 module means that there is no

prescaler for the WDT and vice versa.

The PSA and PS<2:0> bits (OPTION<3:0>) determine

prescaler assignment and prescale ratio.

When assigned to the Timer0 module, all instructions

writing to the TMR0 register (e.g., CLRF 1, MOVWF 1,

BSF 1,x, etc.) will clear the prescaler. When assigned

to WDT, a CLRWDT instruction will clear the prescaler

along with the WDT. The prescaler is neither readable

nor writable. On a Reset, the prescaler contains all ‘0’s.

7.2.1

SWITCHING PRESCALER

ASSIGNMENT

The prescaler assignment is fully under software

control (i.e., it can be changed “on-the-fly” during

program execution). To avoid an unintended device

Reset, the following instruction sequence (Example 7-1)

must be executed when changing the prescaler

assignment from Timer0 to the WDT.

EXAMPLE 7-1:

CHANGING PRESCALER

(TIMER0 WDT)

CLRWDT

;Clear WDT

CLRF TMR0

;Clear TMR0 & Prescaler

MOVLW ‘00xx1111’b ;These 3 lines (5, 6, 7)

OPTION

;are required only if

;desired

CLRWDT

;PS<2:0> are 000 or 001

MOVLW ‘00xx1xxx’b ;Set Postscaler to

OPTION

;desired WDT rate

To change the prescaler from the WDT to the Timer0

module, use the sequence shown in Example 7.2. This

sequence must be used even if the WDT is disabled. A

CLRWDT instruction should be executed before

switching the prescaler.

 2004-2014 Microchip Technology Inc.

DS40001239F-page 29

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