Datasheet

dsPIC30F5011/5013
DS70116J-page 64 © 2011 Microchip Technology Inc.
9.1 Timer Gate Operation
The 16-bit timer can be placed in the Gated Time Accu-
mulation mode. This mode allows the internal T
CY to
increment the respective timer when the gate input sig-
nal (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 the Idle mode, the timer will
stop incrementing unless TSIDL = 0. If TSIDL = 1, the
timer will resume 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
• A device Reset, such as a POR and a BOR
However, if the timer is disabled (TON = 0), then the
timer prescaler cannot be reset since the prescaler
clock is halted.
The TMR1 register is not cleared when the T1CON
register is written. It is cleared by writing to the TMR1
register.
9.3 Timer Operation During Sleep
Mode
During CPU Sleep mode, the timer will operate 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 will con-
tinue to count up to the Period register and be reset to
0x0000.
When a match between the timer and the Period regis-
ter occurs, an interrupt can be generated if the
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
will be 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 will also be generated on the falling edge of
the gate signal (at the end of the accumulation cycle).
Enabling an interrupt is accomplished via the respec-
tive timer interrupt enable bit, T1IE. The timer interrupt
enable bit is located in the IEC0 Control register in the
interrupt controller.
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
9.5.1 RTC OSCILLATOR OPERATION
When TON = 1, TCS = 1 and TGATE = 0, the timer
increments on the rising edge of the 32 kHz LP oscilla-
tor output signal, up to the value specified in the Period
register and is then reset to ‘0’.
The TSYNC bit must be asserted to a logic ‘0’
(Asynchronous mode) for correct operation.
Enabling LPOSCEN (OSCCON<1>) will disable the
normal Timer and Counter modes and enable a timer
carry-out wake-up event.
When the CPU enters Sleep mode, the RTC will con-
tinue to operate provided the 32 kHz external crystal
oscillator is active and the control bits have not been
changed. The TSIDL bit should be cleared to ‘0’ in
order for RTC to continue operation in Idle mode.
9.5.2 RTC INTERRUPTS
When an interrupt event occurs, the respective
interrupt flag, T1IF, is asserted and an interrupt will be
generated if enabled. The T1IF bit must be cleared in
software. The respective Timer interrupt flag, T1IF, is
located in the IFS0 Status register in the interrupt
controller.
Enabling an interrupt is accomplished via the
respective timer interrupt enable bit, T1IE. The timer
interrupt enable bit is located in the IEC0 Control
register in the interrupt controller.
SOSCI
SOSCO
R
C1
C2
dsPIC30FXXXX
32.768 kHz
XTAL
C1 = C2 = 18 pF; R = 100K