PIC12C672 MICROCHIP [Microchip Technology], PIC12C672 Datasheet - Page 25

• Manufacturer Part Number: PIC12C672
• Description: 8-Pin, 8-Bit CMOS Microcontroller with EEPROM Data Memory
• Manufacturer: MICROCHIP [Microchip Technology]

7.0
The Timer0 module has the following features:
• 8-bit timer/counter register, TMR0
• 8-bit software programmable prescaler
• Internal or external clock select
Figure 7-1 is a simplified block diagram of the Timer0
module.
Timer mode is selected by clearing the T0CS bit
(OPTION<5>). In timer mode, the Timer0 module will
increment every instruction cycle (without prescaler). If
TMR0 register is written, the increment is inhibited for
the following two cycles (Figure 7-2 and Figure 7-3).
The user can work around this by writing an adjusted
value to the TMR0 register.
FIGURE 7-1:
1997 Microchip Technology Inc.
- Readable and writable
- Edge select for external clock
GP2/T0CKI
TIMER0 MODULE AND
TMR0 REGISTER
Pin
T0SE
TIMER0 BLOCK DIAGRAM
Note 1: Bits T0CS, T0SE, PSA, PS2, PS1 and PS0 are located in the OPTION register.
F
OSC
2: The prescaler is shared with the Watchdog Timer (Figure 7-5).
/4
T0CS
0
1
(1)
PS2, PS1, PS0
Programmable
Prescaler
Preliminary
3
(2)
(1)
Counter mode is selected by setting the T0CS bit
(OPTION<5>). In this mode, Timer0 will increment
either on every rising or falling edge of pin T0CKI. The
T0SE bit (OPTION<4>) determines the source edge.
Clearing the T0SE bit selects the rising edge.
Restrictions on the external clock input are discussed
in detail in Section 7.1.
The prescaler may be used by either the Timer0
module or the Watchdog Timer, but not both. The
prescaler assignment is controlled in software by the
control bit PSA (OPTION<3>). Clearing the PSA bit
will assign the prescaler to Timer0. The prescaler is
not readable or writable. When the prescaler is
assigned to the Timer0 module, prescale values of 1:2,
1:4,..., 1:256 are selectable. Section 7.2 details the
operation of the prescaler.
A summary of registers associated with the Timer0
module is found in Table 7-1.
PSA
1
0
(1)
PSout
(2 cycle delay)
Sync with
Internal
Clocks
PIC12CE5XX
PSout
Sync
TMR0 reg
Data bus
DS40172A-page 25
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