DSPIC30F5015 datasheet(89/236 Pages) MICROCHIP

89 / 236 page

DS70135E-page 87

dsPIC30F4011/4012

14.3

Position Measurement Mode

There are two Measurement modes which are sup-

ported and are termed x2 and x4. These modes are

selected by the QEIM<2:0> (QEICON<10:8>) mode

select bits.

When control bits, QEIM<2:0> = 100 or 101, the x2

Measurement mode is selected and the QEI logic only

looks at the Phase A input for the position counter

increment rate. Every rising and falling edge of the

Phase A signal causes the position counter to be incre-

mented or decremented. The Phase B signal is still

utilized for the determination of the counter direction

just as in the x4 mode.

Within the x2 Measurement mode, there are two

variations of how the position counter is reset:

Position counter reset by detection of index

pulse, QEIM<2:0> = 100.

Position counter reset by match with MAXCNT,

QEIM<2:0> = 101.

When control bits, QEIM<2:0> = 110 or 111, the x4

Measurement mode is selected and the QEI logic looks

at both edges of the Phase A and Phase B input sig-

nals. Every edge of both signals causes the position

counter to increment or decrement.

Within the x4 Measurement mode, there are two

variations of how the position counter is reset:

Position counter reset by detection of index

pulse, QEIM<2:0> = 110.

Position counter reset by match with MAXCNT,

QEIM<2:0> = 111.

The x4 Measurement mode provides for finer resolu-

tion data (more position counts) for determining motor

position.

14.4

Programmable Digital Noise

Filters

The digital noise filter section is responsible for reject-

ing noise on the incoming capture or quadrature

signals. Schmitt Trigger inputs and a three-clock cycle

delay filter combine to reject low-level noise and large,

short duration, noise spikes that typically occur in noise

prone applications, such as a motor system.

The filter ensures that the filtered output signal is not

permitted to change until a stable value has been

registered for three consecutive clock cycles.

For the QEA, QEB and INDX pins, the clock divide

frequency for the digital filter is programmed by bits

QECK<2:0> (DFLTCON<6:4>) and are derived from

the base instruction cycle TCY.

To enable the filter output for channels QEA, QEB and

INDX, the QEOUT bit must be ‘1’. The filter network for

all channels is disabled on POR and BOR.

14.5

Alternate 16-bit Timer/Counter

When the QEI module is not configured for the QEI

mode, QEIM<2:0> = 001, the module can be config-

ured as a simple 16-bit timer/counter. The setup and

control of the auxiliary timer is accomplished through

the QEICON SFR register. This timer functions identi-

cally to Timer1. The QEA pin is used as the timer clock

input.

When configured as a timer, the POSCNT register

serves as the Timer Count register and the MAXCNT

Period register match occurs, the QEI interrupt flag will

be asserted.

The only exception between the general purpose tim-

ers and this timer is the added feature of external up/

down input select. When the UPDN pin is asserted

high, the timer will increment up. When the UPDN pin

is asserted low, the timer will be decremented.

The UPDN control/status bit (QEICON<11>) can be

used to select the count direction state of the Timer

UPDN = 0, the timer will count down.

In addition, control bit, UPDN_SRC (QEICON<0>),

determines whether the timer count direction state is

based on the logic state written into the UPDN control/

status bit (QEICON<11>) or the QEB pin state. When

UPDN_SRC = 1, the timer count direction is controlled

from the QEB pin. Likewise, when UPDN_SRC = 0, the

timer count direction is controlled by the UPDN bit.

14.6

QEI Module Operation During CPU

Sleep Mode

14.6.1

QEI OPERATION DURING CPU

SLEEP MODE

The QEI module will be halted during the CPU Sleep

mode.

14.6.2

TIMER OPERATION DURING CPU

SLEEP MODE

During CPU Sleep mode, the timer will not operate

because the internal clocks are disabled.

Note:

Changing the operational mode (i.e., from

QEI to timer or vice versa) will not affect the

Timer/Position Count register contents.

Note:

This timer does not support the External

Asynchronous Counter mode of operation.

If using an external clock source, the clock

will automatically be synchronized to the

internal instruction cycle.

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