dsPIC30F Family Reference Manual
DS70059C-page 12-16 © 2004 Microchip Technology Inc.
12.9 32-bit Timer Configuration
A 32-bit timer module can be formed by combining a Type B and a Type C 16-bit timer module.
The Type C time base becomes the MSWord of the combined timer and the Type B time base is
the LSWord.
When configured for 32-bit operation, the control bits for the Type B time base control the operation
of the 32-bit timer. The control bits in the TxCON register for the Type C time base have no effect.
For interrupt control, the combined 32-bit timer uses the interrupt enable, interrupt flag and
interrupt priority control bits of the Type C time base. The interrupt control and status bits for the
Type B time base are not used during 32-bit timer operation.
The following configuration settings assume Timer3 is a Type C time base and Timer2 is a Type B
time base:
• TON (T2CON<15>) = 1.
• T32 (T2CON<3>) = 1.
• TCKPS<1:0> (T2CON<5:4>) are used to set the Prescaler mode for Timer2
(Type B time base).
• The TMR3:TMR2 register pair contains the 32-bit value of the timer module; the TMR3
(Type C time base) register is the Most Significant Word, while the TMR2 (Type B time
base) register is the Least Significant Word of the 32-bit timer value.
• The PR3:PR2 register pair contains the 32-bit period value that is used for comparison with
the TMR3:TMR2 timer value.
• T3IE (IEC0<7>) is used to enable the 32-bit timer interrupt for this configuration.
• T3IF (IFS0<7>) is used as a status flag for the timer interrupt.
• T3IP<2:0> (IPC1<14:12>) sets the interrupt priority level for the 32-bit timer.
• T3CON<15:0> are “don’t care” bits.
A block diagram representation of the 32-bit timer module using Timer2 and Timer3 as an
example is shown in Figure 12-6.
Note: Refer to the device data sheet for information on the specific Type B and Type C
time bases that can be combined.
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