DSPIC30F6010_06 datasheet(74/222 Pages) MICROCHIP

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dsPIC30F6010

DS70119E-page 72

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

Each capture 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

capture 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

processing 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 capture module can only function as an external

interrupt source.

The capture module must be configured for interrupt

only on the 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 are 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.

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