PIC18F44J50-I Datasheet, PDF (203/562 Pages) Microchip Technology – 28/44-Pin, Low-Power, High-Performance USB Microcontrollers

PIC18F46J50 FAMILY
13.2 Timer1 Operation
The Timer1 module is an 8-bit or 16-bit incrementing
counter, which is accessed through the
TMR1H:TMR1L register pair.
When used with an internal clock source, the module is
a timer and increments on every instruction cycle.
When used with an external clock source, the module
can be used as either a timer or counter and
increments on every selected edge of the external
source.
Timer1 is enabled by configuring the TMR1ON and
TMR1GE bits in the T1CON and T1GCON registers,
respectively.
When Timer1 is enabled, the RC1/T1OSI/UOE/RP12
and RC0/T1OSO/T1CKI/RP11 pins become inputs.
This means the values of TRISC<1:0> are ignored and
the pins are read as ‘0’.
13.3 Clock Source Selection
The TMR1CS<1:0> and T1OSCEN bits of the T1CON
register are used to select the clock source for Timer1.
Register 13-1 displays the clock source selections.
13.3.1 INTERNAL CLOCK SOURCE
When the internal clock source is selected, the
TMR1H:TMR1L register pair will increment on multiples
of FOSC as determined by the Timer1 prescaler.
13.3.2 EXTERNAL CLOCK SOURCE
When the external clock source is selected, the Timer1
module may work as a timer or a counter.
When enabled to count, Timer1 is incremented on the
rising edge of the external clock input, T1CKI, or the
capacitive sensing oscillator signal. Either of these
external clock sources can be synchronized to the
microcontroller system clock or they can run
asynchronously.
When used as a timer with a clock oscillator, an
external 32.768 kHz crystal can be used in conjunction
with the dedicated internal oscillator circuit.
Note:
In Counter mode, a falling edge must be
registered by the counter prior to the first
incrementing rising edge after any one or
more of the following conditions:
• Timer1 is enabled after a POR
• Write to TMR1H or TMR1L
• Timer1 is disabled
• Timer1 is disabled (TMR1ON = 0)
when T1CKI is high, then Timer1 is
enabled (TMR1ON = 1) when T1CKI is
low.
TABLE 13-1: TIMER1 CLOCK SOURCE SELECTION
TMR1CS1
TMR1CS0
T1OSCEN
Clock Source
0
1
x
Clock Source (FOSC)
0
0
x
Instruction Clock (FOSC/4)
1
0
0
External Clock on T1CKI Pin
1
0
1
Oscillator Circuit on T1OSI/T1OSO Pin
 2011 Microchip Technology Inc.
DS39931D-page 203