DVR21 datasheet(161/416 Pages) MICROCHIP

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DS30010118D-page 161

PIC24FJ256GA705 FAMILY

13.0 TIMER2/3

The Timer2/3 module is a 32-bit timer, which can also be

configured as independent, 16-bit timers with selectable

operating modes.

As a 32-bit timer, Timer2/3 can operate in three modes:

• Two Independent 16-Bit Timers with All 16-Bit

Operating modes (except Asynchronous Counter

mode)

• Single 32-Bit Timer

• Single 32-Bit Synchronous Counter

They also support these features:

• Timer Gate Operation

• Selectable Prescaler Settings

• Timer Operation during Idle and Sleep modes

• Interrupt on a 32-Bit Period Register Match

• A/D Event Trigger (on Timer2/3 in 32-bit mode

and Timer3 in 16-bit mode)

Individually, all of the 16-bit timers can function as

synchronous timers or counters. They also offer the

features listed above, except for the A/D event trigger.

This trigger is implemented only on Timer2/3 in 32-bit

mode and Timer3 in 16-bit mode. The operating modes

and enabled features are determined by setting the

appropriate bit(s) in the T2CON and T3CON registers.

T2CON is shown in generic form in Register 13-1;

T3CON is shown in Register 13-2.

For 32-bit timer/counter operation, Timer2 is the least

significant word; Timer3 is the most significant word of

the 32-bit timer.

To configure Timer2/3 for 32-bit operation:

Set the T32 bit (T2CON<3> = 1).

Select the prescaler ratio for Timer2 using the

TCKPS<1:0> bits.

Set the Clock and Gating modes using the TCS

and TGATE bits. If TCS is set to an external

clock, RPINRx (TyCK) must be configured to

an available RPn/RPIn pin. For more informa-

tion, see Section 11.5 “Peripheral Pin Select

(PPS)”.

Load the timer period value. PR3 will contain the

most significant word (msw) of the value, while

PR2 contains the least significant word (lsw).

If interrupts are required, set the interrupt enable

bit, T3IE. Use the priority bits, T3IP<2:0>, to set

the interrupt priority. Note that while Timer2 con-

trols the timer, the interrupt appears as a Timer3

interrupt.

Set the TON bit (= 1).

The timer value, at any point, is stored in the register

pair, TMR<3:2>. TMR3 always contains the most

significant word of the count, while TMR2 contains the

least significant word.

To configure any of the timers for individual 16-bit

operation:

Clear the T32 bit (T2CON<3>).

Select the timer prescaler ratio using the

TCKPS<1:0> bits.

Set the Clock and Gating modes using the TCS

and TGATE bits. See Section 11.5 “Peripheral

Pin Select (PPS)” for more information.

Load the timer period value into the PRx register.

If interrupts are required, set the interrupt enable

bit, TxIE. Use the priority bits, TxIP<2:0>, to set

the interrupt priority.

Set the TON (TxCON<15> = 1) bit.

Note:

This data sheet summarizes the features of

this group of PIC24F devices. It is not

intended to be a comprehensive reference

source. For more information, refer to

the “dsPIC33/PIC24 Family Reference

Manual”, “Timers” (DS39704), which is

available from the Microchip website

(www.microchip.com). The information

in this data sheet supersedes the

information in the FRM.

Note:

For 32-bit operation, T3CON control bits

are ignored. Only T2CON control bits are

used for setup and control. Timer2 clock

and gate inputs are utilized for the 32-bit

timer modules, but an interrupt is

generated with the Timer3 interrupt flags.

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