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
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.
Additional information on timer modules is available in
the PICmicro™ Mid-range MCU Family Reference
Manual (DS33023).
REGISTER 6-1: T1CON: TIMER1 CONTROL REGISTER (ADDRESS 10h)
U-0
—
bit7
U-0
—
R/W-0
R/W-0
R/W-0
R/W-0
T1SYNC
R/W-0
R/W-0
bit0
R = Readable bit
W = Writable bit
U = Unimplemented bit,
read as ‘0’
- n = Value at POR reset
T1CKPS1 T1CKPS0 T1OSCEN
TMR1CS TMR1ON
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:
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
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 (F
OSC
/4)
TMR1ON:
Timer1 On bit
1
= Enables Timer1
0
= Stops Timer1
bit 2:
bit 0:
©
1999 Microchip Technology Inc.
DS30292B-page 51
ETC [ ETC ]
