PIC16F87X datasheet(49/200 Pages) MICROCHIP

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PIC16F87X

Preliminary

DS30292A-page 49

6.0

TIMER1 MODULE

The Timer1 module timer/counter has the following fea-

tures:

• 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 Figure 6-1.

Timer1 can be enabled/disabled by setting/clearing

control bit TMR1ON (T1CON<0>).

Figure 6-3 is a simpliﬁed block diagram of the Timer1

module.

Additional information on timer modules is available in

the

PICmicro™

Mid-Range

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).

FIGURE 6-1:

T1CON: TIMER1 CONTROL REGISTER (ADDRESS 10h)

U-0

R/W-0

—

T1CKPS1 T1CKPS0 T1OSCEN T1SYNC

TMR1CS TMR1ON

R= Readable bit

W= Writable bit

U= Unimplemented bit,

read as ‘0’

- n= Value at POR reset

bit7

bit0

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

1 = Oscillator is enabled

0 = Oscillator is shut off

Note: The oscillator inverter and feedback resistor are turned off to eliminate power drain

bit 2:

T1SYNC: Timer1 External Clock Input Synchronization Control bit

TMR1CS = 1

1 = Do not synchronize external clock input

0 = 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

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

0 = Internal clock (FOSC/4)

bit 0:

TMR1ON: Timer1 On bit

1 = Enables Timer1

0 = Stops Timer1

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