Microchip Technology ARD00385 Data Sheet
PIC18F87K90 FAMILY
DS39957D-page 270
2009-2011 Microchip Technology Inc.
FIGURE 19-16:
SIMPLIFIED STEERING
BLOCK DIAGRAM
BLOCK DIAGRAM
19.4.7.1
Steering Synchronization
The STRSYNC bit of the PSTRxCON register gives the
user two choices for when the steering event will
happen. When the STRSYNC bit is ‘0’, the steering
event will happen at the end of the instruction that
writes to the PSTRxCON register. In this case, the out-
put signal at the Px<D:A> pins may be an incomplete
PWM waveform. This operation is useful when the user
firmware needs to immediately remove a PWM signal
from the pin.
When the STRSYNC bit is ‘1’, the effective steering
update will happen at the beginning of the next PWM
period. In this case, steering on/off the PWM output will
always produce a complete PWM waveform.
Figures
user two choices for when the steering event will
happen. When the STRSYNC bit is ‘0’, the steering
event will happen at the end of the instruction that
writes to the PSTRxCON register. In this case, the out-
put signal at the Px<D:A> pins may be an incomplete
PWM waveform. This operation is useful when the user
firmware needs to immediately remove a PWM signal
from the pin.
When the STRSYNC bit is ‘1’, the effective steering
update will happen at the beginning of the next PWM
period. In this case, steering on/off the PWM output will
always produce a complete PWM waveform.
Figures
and
illustrate the timing diagrams
of the PWM steering depending on the STRSYNC
setting.
setting.
FIGURE 19-17:
EXAMPLE OF STEERING EVENT AT END OF INSTRUCTION (STRSYNC = 0)
FIGURE 19-18:
EXAMPLE OF STEERING EVENT AT BEGINNING OF INSTRUCTION (STRSYNC = 1)
1
0
TRIS
Output Pin
PORT Data
PxA Signal
STRA
1
0
TRIS
Output Pin
PORT Data
STRB
1
0
TRIS
Output Pin
PORT Data
STRC
1
0
TRIS
Output Pin
PORT Data
STRD
Note 1:
PORT outputs are configured as displayed
when the CCPxCON register bits,
PxM<1:0> = 00 and CCP1Mx<3:2> = 11.
when the CCPxCON register bits,
PxM<1:0> = 00 and CCP1Mx<3:2> = 11.
2:
Single PWM output requires setting at least
one of the STRx bits.
one of the STRx bits.
CCPxM1
CCPxM0
CCPxM1
CCPxM0
PWM
P1n = PWM
STRn
P1<D:A>
PORT Data
PWM Period
PORT Data
PWM
PORT Data
P1n = PWM
STRn
P1<D:A>
PORT Data