PIC10F200 Microchip Technology, Inc., PIC10F200 Datasheet - Page 33

• Manufacturer Part Number: PIC10F200
• Description: 6-Pin, 8-Bit Flash Microcontrollersfeatures 6-pin SOT-23 Packaging Precision 4 MHZ Internal Oscillator Baseline Core With 33 Instructions, 2 Stack Levels All Single-cycle Instructions Except For Program Branches Which Are Two Cycles 12-bit Wide
• Manufacturer: Microchip Technology, Inc.

6.1.2
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 6-4 shows the
delay from the external clock edge to the timer
incrementing.
FIGURE 6-4:
6.2
An 8-bit counter is available as a prescaler for the
Timer0 module or as a postscaler for the Watchdog
Timer (WDT), respectively (see Section 9.6 “Watch-
dog Timer (WDT)”). For simplicity, this counter is
being referred to as “prescaler” throughout this data
sheet.
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.
 2004 Microchip Technology Inc.
Note:
Note 1: Delay from clock input change to Timer0 increment is 3 T
External Clock/Prescaler
External Clock Input or
Increment Timer0 (Q4)
Prescaler
Output After Sampling
2: External clock if no prescaler selected; prescaler output otherwise.
3: The arrows indicate the points in time where sampling occurs.
Prescaler Output
TIMER0 INCREMENT DELAY
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.
in measuring the interval between two edges on Timer0 input = ±4 T
TIMER0 TIMING WITH EXTERNAL CLOCK
Timer0
(2)
(3)
Q1 Q2 Q3 Q4
(1)
Preliminary
Q1 Q2 Q3 Q4
T0
PIC10F200/202/204/206
6.2.1
The prescaler assignment is fully under software
control (i.e., it can be changed “on-the-fly” during pro-
gram execution). To avoid an unintended device Reset,
the following instruction sequence (Example 6-1) must
be executed when changing the prescaler assignment
from Timer0 to the WDT.
EXAMPLE 6-1:
CLRWDT
CLRF
MOVLW
OPTION
CLRWDT
MOVLW
OPTION
OSC
to 7 T
Q1 Q2 Q3 Q4
TMR0
‘00xx1111’b ;These 3 lines (5, 6, 7)
‘00xx1xxx’b ;Set Postscaler to
OSC
T0 + 1
OSC
SWITCHING PRESCALER
ASSIGNMENT
(Duration of Q = T
max.
CHANGING PRESCALER
(TIMER0
;Clear WDT
;Clear TMR0 & Prescaler
;are required only if
;desired
;PS<2:0> are 000 or 001
;desired WDT rate
Q1 Q2 Q3 Q4
OSC
T0 + 2
Small pulse
misses sampling
). Therefore, the error
WDT)
DS41239A-page 31