DSPIC30F2012 datasheet(80/205 Pages) MICROCHIP

80 / 205 page

dsPIC30F2011/2012/3012/3013

DS70139E-page 78

10.1

Timer Gate Operation

The 32-bit timer can be placed in the Gated Time Accu-

mulation mode. This mode allows the internal TCY to

increment the respective timer when the gate input sig-

nal (T2CK pin) is asserted high. Control bit, TGATE

(T2CON<6>), must be set to enable this mode. When

in this mode, Timer2 is the originating clock source.

The TGATE setting is ignored for Timer3. The timer

must be enabled (TON = 1) and the timer clock source

set to internal (TCS = 0).

The falling edge of the external signal terminates the

count operation but does not reset the timer. The user

must reset the timer in order to start counting from zero.

10.2

ADC Event Trigger

When a match occurs between the 32-bit timer (TMR3/

TMR2) and the 32-bit combined period register (PR3/

PR2), or between the 16-bit timer TMR3 and the 16-bit

period register PR3, a special ADC trigger event signal

is generated by Timer3.

10.3

Timer Prescaler

The input clock (FOSC/4 or external clock) to the timer

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

selected by control bits, TCKPS<1:0> (T2CON<5:4>

and T3CON<5:4>). For the 32-bit timer operation, the

originating clock source is Timer2. The prescaler oper-

ation for Timer3 is not applicable in this mode. The

prescaler counter is cleared when any of the following

occurs:

• a write to the TMR2/TMR3 register

• a write to the T2CON/T3CON register

• device Reset, such as POR and BOR

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

Timer 2 prescaler cannot be reset since the prescaler

clock is halted.

TMR2/TMR3 is not cleared when T2CON/T3CON is

written.

10.4

Timer Operation During Sleep

Mode

The timer does not operate during CPU Sleep mode

because the internal clocks are disabled.

10.5

Timer Interrupt

The 32-bit timer module can generate an interrupt-on-

period match or on the falling edge of the external gate

signal. When the 32-bit timer count matches the

respective 32-bit period register, or the falling edge of

the external “gate” signal is detected, the T3IF bit

(IFS0<7>) is asserted and an interrupt is generated if

enabled. In this mode, the T3IF interrupt flag is used as

the source of the interrupt. The T3IF bit must be

cleared in software.

Enabling

interrupt

accomplished

via

the

respective timer interrupt enable bit, T3IE (IEC0<7>).

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