PIC10F220EOT MICROCHIP [Microchip Technology], PIC10F220EOT Datasheet - Page 29

• Manufacturer Part Number: PIC10F220EOT
• Description: 6-Pin, 8-Bit Flash Microcontrollers
• Manufacturer: MICROCHIP [Microchip Technology]

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 mod-
ule 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 8.6 “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
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.
© 2006 Microchip Technology Inc.
External Clock/Prescaler
Note:
External Clock Input or
Increment Timer0 (Q4)
Output After Sampling
Note 1: Delay from clock input change to Timer0 increment is 3T
Prescaler Output (2)
to
Prescaler
2: External clock if no prescaler selected; prescaler output otherwise.
3: The arrows indicate the points in time where sampling occurs.
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.
the
Therefore, the error in measuring the interval between two edges on Timer0 input = ±4T
TMR0
Timer0
TIMER0 TIMING WITH EXTERNAL CLOCK
register
(3)
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
(e.g.,
(1)
CLRF 1,
Preliminary
T0
OSC
to 7T
T0 + 1
PIC10F220/222
OSC
. (Duration of Q = T
T0 + 2
DS41270B-page 27
Small pulse
misses sampling
OSC
OSC
max.
).