PIC18F2220 MICROCHIP [Microchip Technology], PIC18F2220 Datasheet - Page 123

• Manufacturer Part Number: PIC18F2220
• Description: 28/40/44-Pin High-Performance, Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

12.0
The Timer1 module timer/counter has the following
features:
• 16-bit timer/counter (two 8-bit registers: TMR1H
• Readable and writable (both registers)
• Internal or external clock select
• Interrupt-on-overflow from FFFFh to 0000h
• Reset from CCP module special event trigger
• Status of system clock operation
Figure 12-1 is a simplified block diagram of the Timer1
module.
REGISTER 12-1:
 2003 Microchip Technology Inc.
and TMR1L)
TIMER1 MODULE
bit 7
bit 6
bit 5-4
bit 3
bit 2
bit 1
bit 0
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
T1RUN: Timer1 System Clock Status bit
1 = System clock is derived from Timer1 oscillator
0 = System clock is derived from another source
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 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.
T1SYNC: Timer1 External Clock Input Synchronization Select bit
When TMR1CS = 1 (External Clock):
1 = Do not synchronize external clock input
0 = Synchronize external clock input
When TMR1CS = 0 (Internal Clock):
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/T13CKI (on the rising edge)
0 = Internal clock (F
TMR1ON: Timer1 On bit
1 = Enables Timer1
0 = Stops Timer1
bit 7
Legend:
R = Readable bit
- n = Value at POR
T1CON: TIMER1 CONTROL REGISTER
R/W-0
RD16
T1RUN
R-0
OSC
T1CKPS1
/4)
PIC18F2220/2320/4220/4320
R/W-0
W = Writable bit
‘1’ = Bit is set
T1CKPS0
R/W-0
Register 12-1 details the Timer1 Control register. This
register controls the operating mode of the Timer1
module and contains the Timer1 Oscillator Enable bit
(T1OSCEN). Timer1 can be enabled or disabled by
setting or clearing control bit, TMR1ON (T1CON<0>).
The Timer1 oscillator can be used as a secondary clock
source in power managed modes. When the T1RUN bit
is set, the Timer1 oscillator is providing the system clock.
If the Fail-Safe Clock Monitor is enabled and the Timer1
oscillator fails while providing the system clock, polling
the T1RUN bit will indicate whether the clock is being
provided by the Timer1 oscillator or another source.
Timer1 can also be used to provide Real-Time Clock
(RTC) functionality to applications with only a minimal
addition of external components and code overhead.
T1OSCEN
R/W-0
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
T1SYNC
R/W-0
TMR1CS
x = Bit is unknown
R/W-0
DS39599C-page 121
TMR1ON
R/W-0
bit 0