DSPIC30F Datasheet, PDF (84/248 Pages) Microchip Technology – dsPIC High-Performance 16-bit Digital Signal Controller Family Overview

dsPIC30F
9.1 Timer Gate Operation
The 16-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 (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
• clearing of the TON bit (T1CON<15>)
• 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
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
C1
SOSCI
32.768 kHz
XTAL
dsPIC30FXXXX
SOSCO
C2
R
C1 = C2 = 18 pF; R = 100K
DS70083G-page 82
Preliminary
 2004 Microchip Technology Inc.