PIC16F72SLASHML datasheet(33/136 Pages) MICROCHIP

33 / 136 page

 2002 Microchip Technology Inc.

DS39597B-page 31

PIC16F72

6.0

TIMER1 MODULE

The Timer1 module timer/counter has the following

features:

• 16-bit timer/counter

(Two 8-bit registers; TMR1H and TMR1L)

• Readable and writable (both registers)

• Internal or external clock select

• Interrupt on overflow from FFFFh to 0000h

• RESET from CCP module trigger

Timer1 has a control register, shown in Register 6-1.

Timer1 can be enabled/disabled by setting/clearing

control bit TMR1ON (T1CON<0>).

Figure 6-2 is a simplified block diagram of the Timer1

module.

Additional information on timer modules is available in

the PICmicro™ Mid-Range MCU Reference Manual,

(DS33023).

6.1

Timer1 Operation

Timer1 can operate in one of these modes:

• As a timer

• As a synchronous counter

• As an asynchronous counter

The Operating mode is determined by the clock select

bit, TMR1CS (T1CON<1>).

In Timer mode, Timer1 increments every instruction

cycle. In Counter mode, it increments on every rising

edge of the external clock input.

When the Timer1 oscillator is enabled (T1OSCEN is

set), the RC1/T1OSI and RC0/T1OSO/T1CKI pins

become inputs. That is, the TRISC<1:0> value is

ignored.

Timer1 also has an internal “RESET input”. This

RESET can be generated by the CCP module

(Section 8.0).

T1CON: TIMER1 CONTROL REGISTER (ADDRESS 10h)

U-0

R/W-0

—

T1CKPS1

T1CKPS0

T1OSCEN T1SYNC TMR1CS

TMR1ON

bit 7

bit 0

bit 7-6

Unimplemented: Read as ‘0’

bit 5-4

T1CKPS1:T1CKPS0: Timer1 Input Clock Prescale Select bits

= 1:8 Prescale value

= 1:4 Prescale value

= 1:2 Prescale value

= 1:1 Prescale value

bit 3

T1OSCEN: Timer1 Oscillator Enable Control bit

= Oscillator is enabled

= Oscillator is shut-off (The oscillator inverter is turned off to eliminate power drain.)

bit 2

T1SYNC: Timer1 External Clock Input Synchronization Control bit

TMR1CS = 1:

= Do not synchronize external clock input

= Synchronize external clock input

TMR1CS = 0:

This bit is ignored. Timer1 uses the internal clock when TMR1CS = ‘0’.

bit 1

TMR1CS: Timer1 Clock Source Select bit

= External clock from pin RC0/T1OSO/T1CKI (on the rising edge)

= Internal clock (FOSC/4)

bit 0

TMR1ON: Timer1 On bit

= Enables Timer1

= Stops Timer1

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

- n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

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