PIC18LF4331 datasheet(158/392 Pages) MICROCHIP

158 / 392 page

PIC18F2331/2431/4331/4431

DS39616D-page 158

 2010 Microchip Technology Inc.

17.1.3.1

Pulse-Width Measurement Timing

Pulse-width measurement accuracy can only be

ensured when the pulse-width high and low present on

the CAPx input exceeds one TCY clock cycle. The

limitations depend on the mode selected:

• When CAPxM<3:0> = 0110 (rising to falling edge

delay), the CAPx input high pulse width (TCCH)

must exceed TCY + 10 ns.

• When CAPxM<3:0> = 0111 (falling to rising edge

delay), the CAPx input low pulse width (TCCL)

must exceed TCY + 10 ns.

17.1.4

INPUT CAPTURE ON STATE

CHANGE

When CAPxM<3:0> = 1000, the value is captured on

every signal change on the CAPx input. If all three

capture channels are configured in this mode, the three

input captures can be used as the Hall effect sensor

state transition detector. The value of Timer5 can be

captured, Timer5 reset and the interrupt generated.

Any change on CAP1, CAP2 or CAP3 is detected and

the associated time base count is captured.

For position and velocity measurement in this mode,

the timer can be optionally reset (see Section 17.1.6

“Timer5 Reset”

for Reset options).

FIGURE 17-6:

INPUT CAPTURE ON STATE CHANGE (HALL EFFECT SENSOR MODE)

Note 1:

The Period Measurement mode will

produce valid results upon sampling of the

second rising edge of the input capture.

CAPxBUF values latched during the first

active edge after initialization are invalid.

The Pulse-Width Measurement mode will

latch the value of the timer upon sampling

of the first input signal edge by the input

capture.

CAP2

CAP1

CAP3

Time Base(1)

CAP1BUF(2)

CAP2BUF(2)

CAP3BUF(2)

0FFFh

0000h

Time Base Reset(1)

Note 1:

TMR5 can be selected as the time base for input capture. The time base can be optionally reset when the Capture

Reset Enable bit is set (CAPxREN = 1).

Detailed CAPxBUF event timing (all modes reflect the same capture and Reset timing) is shown in Figure 17-4. There

are six commutation BLDC Hall effect sensor states shown. The other two remaining states (i.e., 000h and 111h) are

invalid in the normal operation. They remain to be decoded by the CPU firmware in BLDC motor application.

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