Microchip Technology DM164134 Data Sheet
© 2006 Microchip Technology Inc.
DS41159E-page 113
PIC18FXX8
12.0
TIMER1 MODULE
The Timer1 module timer/counter has the following
features:
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 special event trigger
Register 12-1 shows the Timer1 Control register. This
register controls the operating mode of the Timer1
module, as well as contains the Timer1 Oscillator
Enable bit (T1OSCEN). Timer1 can be enabled/
disabled by setting/clearing control bit, TMR1ON
(T1CON register).
register controls the operating mode of the Timer1
module, as well as contains the Timer1 Oscillator
Enable bit (T1OSCEN). Timer1 can be enabled/
disabled by setting/clearing control bit, TMR1ON
(T1CON register).
Figure 12-1 is a simplified block diagram of the Timer1
module.
module.
REGISTER 12-1:
T1CON: TIMER1 CONTROL REGISTER
Note:
Timer1 is disabled on POR.
R/W-0
U-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
RD16
—
T1CKPS1 T1CKPS0 T1OSCEN
T1SYNC
TMR1CS
TMR1ON
bit 7
bit 0
bit 7
RD16: 16-bit Read/Write Mode Enable bit
1
= Enables register read/write of Timer1 in one 16-bit operation
0
= Enables register read/write of Timer1 in two 8-bit operations
bit 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 bit
1
= Timer1 oscillator is enabled
0
= Timer1 oscillator is shut-off
The oscillator inverter and feedback resistor are turned off to eliminate power drain.
bit 2
T1SYNC: Timer1 External Clock Input Synchronization Select 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.
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)
bit 0
TMR1ON: Timer1 On bit
1
= Enables Timer1
0
= 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