PIC18F2331 Datasheet, PDF (168/396 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers with nanoWatt Technology, High Performance PWM and A/D

PIC18F2331/2431/4331/4431
16.1.3.1 Pulse Width Measurement Timing
Pulse width measurement accuracy can be only
ensured when the pulse width high and low present on
CAPx input exceeds one TCY clock cycle. The
limitations depend on the mode selected:
• When CAPxM3:CAPxM0 = 0110 (rising-to-falling
edge delay), the CAPx input high pulse width
(TccH) must exceed TCY + 10 ns.
• When CAPxM3:CAPxM0 = 0111 (falling-to-rising
edge delay), the CAPx input low pulse width
(TccL) must exceed TCY + 10 ns.
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.
2: The Pulse Width Measurement mode will
latch the value of the timer upon sampling
of the first input signal edge by the input
capture.
16.1.4 INPUT CAPTURE ON STATE
CHANGE
When CAPxM3:CAPxM0 = 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-capture 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 16.1.6
“Timer5 Reset” for Reset options).
FIGURE 16-6:
INPUT CAPTURE ON STATE CHANGE (HALL-EFFECT SENSOR MODE)
CAP1
CAP2
CAP3
0FFFh
Time Base⁽¹⁾
0000h
CAP1BUF⁽²⁾
CAP2BUF⁽²⁾
CAP3BUF⁽²⁾
Time Base Reset⁽¹⁾
11 1 0
00 1 1
10 0 0
00
10
11
Note 1: TMR5 can be selected as the time base for input capture. Time base can be optionally reset when the capture reset
enabled bit is set (CAPXREN = 1).
2: Detailed CAPxBUF event timing (all modes reflect same capture and Reset timing) is shown in Figure 16-4.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 are still to be decoded by the CPU firmware in BLDC motor application.
DS39616B-page 166
Preliminary
 2003 Microchip Technology Inc.