PIC16F877-20L Datasheet, PDF (51/218 Pages) Microchip Technology – 28/40-Pin 8-Bit CMOS FLASH Microcontrollers

PIC16F87X
6.0 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 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>).
In Timer mode, Timer1 increments every instruction
cycle. In Counter mode, it increments on every rising
edge of the external clock input.
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 either of the two CCP
modules (Section 8.0). Register 6-1 shows the Timer1
control register.
When the Timer1 oscillator is enabled (T1OSCEN is
set), the RC1/T1OSI/CCP2 and RC0/T1OSO/T1CKI
pins become inputs. That is, the TRISC<1:0> value is
ignored, and these pins read as ‘0’.
Additional information on timer modules is available in
the PIC^® MCU Mid-Range Family Reference Manual
(DS33023).
REGISTER 6-1:
T1CON: TIMER1 CONTROL REGISTER (ADDRESS 10h)
U-0
—
bit 7
U-0
R/W-0 R/W-0
R/W-0
R/W-0 R/W-0 R/W-0
— T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON
bit 0
bit 7-6
bit 5-4
bit 3
bit 2
bit 1
bit 0
Unimplemented: Read as '0'
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
T1OSCEN: Timer1 Oscillator Enable Control bit
1 = Oscillator is enabled
0 = Oscillator is shut-off (the oscillator inverter is turned off to eliminate power drain)
T1SYNC: Timer1 External Clock Input Synchronization Control bit
When TMR1CS = 1:
1 = Do not synchronize external clock input
0 = Synchronize external clock input
When TMR1CS = 0:
This bit is ignored. Timer1 uses the internal clock when TMR1CS = 0.
TMR1CS: Timer1 Clock Source Select bit
1 = External clock from pin RC0/T1OSO/T1CKI (on the rising edge)
0 = Internal clock (FOSC/4)
TMR1ON: Timer1 On bit
1 = Enables Timer1
0 = Stops Timer1
Legend:
R = Readable bit
- n = Value at POR
W = Writable bit
’1’ = Bit is set
U = Unimplemented bit, read as ‘0’
’0’ = Bit is cleared x = Bit is unknown
 1998-2013 Microchip Technology Inc.
DS30292D-page 51