PIC16F753 Datasheet, PDF (64/238 Pages) Microchip Technology – 14/16-Pin, Flash-Based 8-Bit CMOS Microcontrollers

PIC16F753/HV753
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. Table 7-1 displays the Timer1 enable
selections.
TABLE 7-1:
TMR1ON
0
0
1
1
TIMER1 ENABLE
SELECTIONS
TMR1GE
Timer1
Operation
0
Off
1
Off
0
Always On
1
Count Enabled
7.2 Clock Source Selection
The TMR1CS<1:0> bits of the T1CON register are used
to select the clock source for Timer1. Table 7-2 displays
the clock source selections.
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)
7.2.1 INTERNAL CLOCK SOURCE
When the internal clock source is selected, the
TMR1H:TMR1L register pair will increment on multiples
of FOSC 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.
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.
7.2.3 WDT OSCILLATOR
When the Watchdog is selected, Timer 1 will use the
LFINTOSC that is used to operate the Watchdog
Timer. This is the same oscillator as the LFINTOSC
used as the system clock. Selecting this option will
enable the oscillator even when the LFINTOSC or the
Watchdog are not in use. This oscillator will continue
to operate when in Sleep mode.
DS40001709A-page 64
Preliminary
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