
2002 Microchip Technology Inc.
Preliminary
DS30485A-page 103
PIC18FXX39
11.0 TIMER1 MODULE
The Timer1 module timer/counter has the following
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
Figure 11-1 is a simplified block diagram of the Timer1
module.
sets the Operating mode of the Timer1 module. Timer1
can be enabled or disabled by setting or clearing
control bit TMR1ON (T1CON<0>).
REGISTER 11-1:
T1CON: TIMER1 CONTROL REGISTER
R/W-0
U-0
R/W-0
U-0
R/W-0
RD16
—
T1CKPS1 T1CKPS0
—
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
Unimplemented: Maintain as '0'
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.
bit 1
TMR1CS: Timer1 Clock Source Select bit
1
= External clock from pin RC0/T13CKI (on the rising edge)
0
= Internal clock (FOSC/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