PIC16F62X
In timer mode, Timer1 increments every instruction
cycle. In counter mode, it increments on every rising
edge of the external clock input.
7.0
TIMER1 MODULE
The Timer1 module is a 16-bit timer/counter consisting
of two 8-bit registers (TMR1H and TMR1L) which are
readable and writable. The TMR1 Register pair
(TMR1H:TMR1L) increments from 0000h to FFFFh
and rolls over to 0000h. The TMR1 Interrupt, if enabled,
is generated on overflow which is latched in interrupt
flag bit TMR1IF (PIR1<0>). This interrupt can be
enabled/disabled by setting/clearing TMR1 interrupt
enable bit TMR1IE (PIE1<0>).
Timer1 can be enabled/disabled by setting/clearing
control bit TMR1ON (T1CON<0>).
Timer1 also has an internal “reset input”. This reset can
be generated by the CCP module (Section 10.0).
Register 7-1 shows the Timer1 control register.
For the PIC16F627 and PIC16F628, when the Timer1
oscillator is enabled (T1OSCEN is set), the RB7/T1OSI
and RB6/T1OSO/T1CKI pins become inputs. That is,
the TRISB<7:6> value is ignored.
Timer1 can operate in one of two modes:
• As a timer
• As a counter
The operating mode is determined by the clock select
bit, TMR1CS (T1CON<1>).
REGISTER 7-1: T1CON: TIMER1 CONTROL REGISTER (ADDRESS 10h)
U-0
—
U-0
—
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R = Readable bit
W = Writable bit
U = Unimplemented bit,
read as ‘0’
T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON
bit0
bit7
- n = Value at POR reset
bit 7-6: Unimplemented: Read as '0'
bit 5-4: T1CKPS1:T1CKPS0: Timer1 Input Clock Prescale Select bits
11= 1:8 Prescale value
10= 1:4 Prescale value
01= 1:2 Prescale value
00= 1:1 Prescale value
bit 3:
bit 2:
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
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:
bit 0:
TMR1CS: Timer1 Clock Source Select bit
1= External clock from pin RB6/T1OSO/T1CKI (on the rising edge)
0= Internal clock (FOSC/4)
TMR1ON: Timer1 On bit
1= Enables Timer1
0= Stops Timer1
DS40300B-page 50
Preliminary
1999 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
