PIC16C505T-20I/SL データシートの表示（PDF） - Microchip Technology

部品番号

コンポーネント説明

メーカー

PIC16C505T-20I/SL

14-Pin, 8-Bit CMOS Microcontroller

Microchip Technology 

6.0 TIMER0 MODULE AND TMR0

REGISTER

The Timer0 module has the following features:

• 8-bit timer/counter register, TMR0

- Readable and writable

• 8-bit software programmable prescaler

• Internal or external clock select

- Edge select for external clock

Figure 6-1 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 6-2 and Figure 6-3).

The user can work around this by writing an adjusted

value to the TMR0 register.

PIC16C505

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 6.1.

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 6.2 details the

operation of the prescaler.

A summary of registers associated with the Timer0

module is found in Table 6-1.

FIGURE 6-1: TIMER0 BLOCK DIAGRAM

RC5/T0CKI

Pin

FOSC/4

T0SE

Data Bus

0

PSout

8

1

Sync with

1

Internal

TMR0 reg

Programmable

Prescaler(2)

0

Clocks

PSout

(2 TCY delay) Sync

T0CS(1)

3

PS2, PS1, PS0(1)

PSA(1)

Note 1: Bits T0CS, T0SE, PSA, PS2, PS1 and PS0 are located in the OPTION register.

2: The prescaler is shared with the Watchdog Timer (Figure 6-5).

© 1999 Microchip Technology Inc.

DS40192C-page 23

Share Link: