Datasheet

PIC12F752/HV752
DS41576B-page 60 Preliminary  2011 Microchip Technology Inc.
7.1 Timer1 Operation
The Timer1 module is a 16-bit incrementing counter
which is accessed through the TMR1H:TMR1L register
pair. Writes to TMR1H or TMR1L directly update the
counter.
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. Ta b le 7 - 1 displays the Timer1 enable
selections.
7.2 Clock Source Selection
The TMR1CS<1:0> bits of the T1CON register are used
to select the clock source for Timer1. Tabl e 7-2 displays
the clock source selections.
7.2.1 INTERNAL CLOCK SOURCE
When the internal clock source is selected, the
TMR1H:TMR1L register pair will increment on multiples
of F
OSC or FOSC/4 as determined by the Timer1
prescaler.
7.2.2 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.
7.2.3 TEMPERATURE SENSE
OSCILLATOR
When the Temperature Sense Oscillator source is
selected, the TMR1H:TMR1L register pair will increment
on multiples of the Temperature Sense Oscillator as
determined by the Timer1 prescaler. The Temperature
Sense Oscillator operates at 16 kHz typical.
TABLE 7-1: TIMER1 ENABLE
SELECTIONS
TMR1ON TMR1GE
Timer1
Operation
00Off
01Off
10Always On
11Count Enabled
TABLE 7-2: CLOCK SOURCE
SELECTIONS
TMR1CS<1:0> Clock Source
11 Temperature Sense Oscillator
10 External Clocking on T1CKI Pin
01 System Clock (FOSC)
00 Instruction Clock (FOSC/4)
Note: In Counter mode, a falling edge must be
registered by the counter prior to the first
incrementing rising edge (see Figure 7-2)
after any one or more of the following
conditions:
• Timer1 enabled after POR Reset
• 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.