DSPIC30F5011_07 Datasheet, PDF (82/224 Pages) Microchip Technology – High-Performance, 16-bit Digital Signal Controllers

dsPIC30F5011/5013
12.1.2 CAPTURE BUFFER OPERATION
Each capture channel has an associated FIFO buffer
which is four 16-bit words deep. There are two status
flags which provide status on the FIFO buffer:
• ICBFNE – Input Capture Buffer Not Empty
• ICOV – Input Capture Overflow
The ICBFNE will be set on the first input capture event
and remain set until all capture events have been read
from the FIFO. As each word is read from the FIFO, the
remaining words are advanced by one position within
the buffer.
In the event that the FIFO is full with four capture
events and a fifth capture event occurs prior to a read
of the FIFO, an overflow condition will occur and the
ICOV bit will be set to a logic ‘1’. The fifth capture event
is lost and is not stored in the FIFO. No additional
events will be captured until all four events have been
read from the buffer.
If a FIFO read is performed after the last read and no
new capture event has been received, the read will
yield indeterminate results.
12.1.3 TIMER2 AND TIMER3 SELECTION
MODE
The input capture module consists of up to 8 input cap-
ture channels. Each channel can select between one of
two timers for the time base, Timer2 or Timer3.
Selection of the timer resource is accomplished
through SFR bit, ICTMR (ICxCON<7>). Timer3 is the
default timer resource available for the input capture
module.
12.1.4 HALL SENSOR MODE
When the input capture module is set for capture on
every edge, rising and falling, ICM<2:0> = 001, the fol-
lowing operations are performed by the input capture
logic:
• The input capture interrupt flag is set on every
edge, rising and falling.
• The interrupt on Capture mode setting bits,
ICI<1:0>, is ignored since every capture
generates an interrupt.
• A capture overflow condition is not generated in
this mode.
12.2 Input Capture Operation During
Sleep and Idle Modes
An input capture event will generate a device wake-up
or interrupt, if enabled, if the device is in CPU Idle or
Sleep mode.
Independent of the timer being enabled, the input cap-
ture module will wake-up from the CPU Sleep or Idle
mode when a capture event occurs if ICM<2:0> = 111
and the interrupt enable bit is asserted. The same wake-
up can generate an interrupt if the conditions for pro-
cessing the interrupt have been satisfied. The wake-up
feature is useful as a method of adding extra external pin
interrupts.
12.2.1 INPUT CAPTURE IN CPU SLEEP
MODE
CPU Sleep mode allows input capture module opera-
tion with reduced functionality. In the CPU Sleep mode,
the ICI<1:0> bits are not applicable and the input cap-
ture module can only function as an external interrupt
source.
The capture module must be configured for interrupt
only on rising edge (ICM<2:0> = 111) in order for the
input capture module to be used while the device is in
Sleep mode. The prescale settings of 4:1 or 16:1 are
not applicable in this mode.
12.2.2 INPUT CAPTURE IN CPU IDLE
MODE
CPU Idle mode allows input capture module operation
with full functionality. In the CPU Idle mode, the Inter-
rupt mode selected by the ICI<1:0> bits is applicable,
as well as the 4:1 and 16:1 capture prescale settings
which are defined by control bits ICM<2:0>. This mode
requires the selected timer to be enabled. Moreover,
the ICSIDL bit must be asserted to a logic ‘0’.
If the input capture module is defined as
ICM<2:0> = 111 in CPU Idle mode, the input capture
pin will serve only as an external interrupt pin.
12.3 Input Capture Interrupts
The input capture channels have the ability to generate
an interrupt based upon the selected number of cap-
ture events. The selection number is set by control bits
ICI<1:0> (ICxCON<6:5>).
Each channel provides an interrupt flag (ICxIF) bit. The
respective capture channel interrupt flag is located in
the corresponding IFSx Status register.
Enabling an interrupt is accomplished via the respec-
tive capture channel interrupt enable (ICxIE) bit. The
capture interrupt enable bit is located in the
corresponding IEC Control register.
DS70116G-page 80
© 2007 Microchip Technology Inc.