dsPIC30F2011 datasheet(74/206 Pages) MICROCHIP

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dsPIC30F2011/2012/3012/3013

DS70139F-page 74

9.1

Timer Gate Operation

The 16-bit timer can be placed in the Gated Time

Accumulation mode. This mode allows the internal TCY

to increment the respective timer when the gate input

signal (T1CK pin) is asserted high. Control bit,

TGATE (T1CON<6>), must be set to enable this mode.

The timer must be enabled (TON = 1) and the timer

clock source set to internal (TCS = 0).

When the CPU goes into Idle mode, the timer stops

incrementing unless TSIDL = 0. If TSIDL = 1, the timer

resumes the incrementing sequence upon termination

of the CPU Idle mode.

9.2

Timer Prescaler

The input clock (FOSC/4 or external clock) to the 16-bit

Timer has a prescale option of 1:1, 1:8, 1:64 and 1:256,

selected by control bits, TCKPS<1:0> (T1CON<5:4>).

The prescaler counter is cleared when any of the

following occurs:

• a write to the TMR1 register

• a write to the T1CON register

• device Reset, such as POR and BOR

However, if the timer is disabled (TON = 0), then the

timer prescaler cannot be reset since the prescaler

clock is halted.

TMR1 is not cleared when T1CON is written. It is

cleared by writing to the TMR1 register.

9.3

Timer Operation During Sleep

Mode

The timer operates during CPU Sleep mode, if:

• The timer module is enabled (TON = 1), and

• The timer clock source is selected as external

(TCS = 1), and

• The TSYNC bit (T1CON<2>) is asserted to a logic

‘0’ which defines the external clock source as

asynchronous.

When all three conditions are true, the timer continues

to count up to the Period register and be reset to

0x0000.

When a match between the timer and the Period

respective timer interrupt enable bit is asserted.

9.4

Timer Interrupt

The 16-bit timer has the ability to generate an

interrupt-on-period match. When the timer count

matches the Period register, the T1IF bit is asserted and

an interrupt is generated, if enabled. The T1IF bit must be

cleared in software. The timer interrupt flag, T1IF, is

located in the IFS0 Control register in the interrupt

controller.

When the Gated Time Accumulation mode is enabled,

an interrupt is also generated on the falling edge of the

gate signal (at the end of the accumulation cycle).

Enabling an interrupt is accomplished via the

respective timer interrupt enable bit, T1IE. The timer

interrupt enable bit is located in the IEC0 Control

9.5

Real-Time Clock

Timer1, when operating in Real-Time Clock (RTC)

mode, provides time of day and event time-stamping

capabilities. Key operational features of the RTC are:

• Operation from 32 kHz LP oscillator

• 8-bit prescaler

• Low power

• Real-Time Clock interrupts

These operating modes are determined by setting the

appropriate bit(s) in the T1CON Control register.

FIGURE 9-2:

RECOMMENDED

COMPONENTS FOR

TIMER1 LP OSCILLATOR

RTC

SOSCI

SOSCO

dsPIC30FXXXX

32.768 kHz

XTAL

C1 = C2 = 18 pF; R = 100K

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