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2011-2015 Microchip Technology Inc.
DS40001609E-page 275
PIC16(L)F1508/9
25.2
Fixed Duty Cycle (FDC) Mode
In Fixed Duty Cycle (FDC) mode, every time the
accumulator overflows (NCO_overflow), the output is
toggled. This provides a 50% duty cycle, provided that
the increment value remains constant. For more
information, see
.
The FDC mode is selected by clearing the NxPFM bit
in the NCOxCON register.
25.3
Pulse Frequency (PF) Mode
In Pulse Frequency (PF) mode, every time the accumu-
lator overflows (NCO_overflow), the output becomes
active for one or more clock periods. Once the clock
period expires, the output returns to an inactive state.
This provides a pulsed output.
The output becomes active on the rising clock edge
immediately following the overflow event. For more
information, see
.
The value of the active and inactive states depends on
the polarity bit, NxPOL in the NCOxCON register.
The PF mode is selected by setting the NxPFM bit in
the NCOxCON register.
25.3.1
OUTPUT PULSE WIDTH CONTROL
When operating in PF mode, the active state of the out-
put can vary in width by multiple clock periods. Various
pulse widths are selected with the NxPWS<2:0> bits in
the NCOxCLK register.
When the selected pulse width is greater than the
accumulator overflow time frame, the output of the
NCOx operation is indeterminate.
25.4
Output Polarity Control
The last stage in the NCOx module is the output polar-
ity. The NxPOL bit in the NCOxCON register selects the
output polarity. Changing the polarity while the inter-
rupts are enabled will cause an interrupt for the result-
ing output transition.
The NCOx output can be used internally by source
code or other peripherals. Accomplish this by reading
the NxOUT (read-only) bit of the NCOxCON register.
The NCOx output signal is available to the following
peripherals:
• CLC
• CWG
25.5
Interrupts
When the accumulator overflows (NCO_overflow), the
NCOx Interrupt Flag bit, NCOxIF, of the PIRx register is
set. To enable the interrupt event (NCO_interrupt), the
following bits must be set:
• NxEN bit of the NCOxCON register
• NCOxIE bit of the PIEx register
• PEIE bit of the INTCON register
• GIE bit of the INTCON register
The interrupt must be cleared by software by clearing
the NCOxIF bit in the Interrupt Service Routine.
25.6
Effects of a Reset
All of the NCOx registers are cleared to zero as the
result of a Reset.
25.7
Operation In Sleep
The NCO module operates independently from the
system clock and will continue to run during Sleep,
provided that the clock source selected remains
active.
The HFINTOSC remains active during Sleep when the
NCO module is enabled and the HFINTOSC is
selected as the clock source, regardless of the system
clock source selected.
In other words, if the HFINTOSC is simultaneously
selected as the system clock and the NCO clock
source, when the NCO is enabled, the CPU will go idle
during Sleep, but the NCO will continue to operate and
the HFINTOSC will remain active.
This will have a direct effect on the Sleep mode current.
25.8
Alternate Pin Locations
This module incorporates I/O pins that can be moved to
other locations with the use of the alternate pin function
register, APFCON. To determine which pins can be
moved and what their default locations are upon a
Reset, see
Section 11.1 “Alternate Pin Function”
for
more information.
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