DSPIC30F datasheet(98/248 Pages) MICROCHIP

98 / 248 page

dsPIC30F

DS70083G-page 96

Preliminary

 2004 Microchip Technology Inc.

12.1

Simple Capture Event Mode

The simple capture events in the dsPIC30F product

family are:

• Capture every falling edge

• Capture every rising edge

• Capture every 4th rising edge

• Capture every 16th rising edge

• Capture every rising and falling edge

These simple Input Capture modes are configured by

setting the appropriate bits ICM<2:0> (ICxCON<2:0>).

12.1.1

CAPTURE PRESCALER

There are four input capture prescaler settings speci-

fied by bits ICM<2:0> (ICxCON<2:0>). Whenever the

capture channel is turned off, the prescaler counter will

be cleared. In addition, any Reset will clear the

prescaler counter.

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.

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