Microchip Technology DM183021 Data Sheet
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 T
ensured when the pulse-width high and low present on
the CAPx input exceeds one T
CY
clock cycle. The
limitations depend on the mode selected:
• When CAPxM<3:0> = 0110 (rising to falling edge
• When CAPxM<3:0> = 0110 (rising to falling edge
delay), the CAPx input high pulse width (T
CC
H)
must exceed T
CY
+ 10 ns.
• When CAPxM<3:0> = 0111 (falling to rising edge
delay), the CAPx input low pulse width (T
CC
L)
must exceed T
CY
+ 10 ns.
17.1.4
INPUT CAPTURE ON STATE
CHANGE
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
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
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.
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.
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)
1
0
1
1
0
0
1
1
0
0
1
0
0
1
1
0
0
1
S
ta
te 1
S
ta
te 2
S
ta
te 3
S
ta
te 4
S
ta
te 5
S
ta
te 6
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).
Reset Enable bit is set (CAPxREN = 1).
2:
Detailed CAPxBUF event timing (all modes reflect the same capture and Reset timing) is shown in
. 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.
invalid in the normal operation. They remain to be decoded by the CPU firmware in BLDC motor application.