Microchip Technology MA240017 数据表
2008-2011 Microchip Technology Inc.
DS39927C-page 125
PIC24F16KA102 FAMILY
15.0
OUTPUT COMPARE
15.1
Setup for Single Output Pulse
Generation
Generation
When the OCM control bits (OC1CON<2:0>) are set to
‘100’, the selected output compare channel initializes
the OC1 pin to the low state and generates a single
output pulse.
To generate a single output pulse, the following steps
are required (these steps assume the timer source is
initially turned off, but this is not a requirement for the
module operation):
1.
‘100’, the selected output compare channel initializes
the OC1 pin to the low state and generates a single
output pulse.
To generate a single output pulse, the following steps
are required (these steps assume the timer source is
initially turned off, but this is not a requirement for the
module operation):
1.
Determine the instruction clock cycle time. Take
into account the frequency of the external clock
to the timer source (if one is used) and the timer
prescaler settings.
into account the frequency of the external clock
to the timer source (if one is used) and the timer
prescaler settings.
2.
Calculate time to the rising edge of the output
pulse relative to the TMRy start value (0000h).
pulse relative to the TMRy start value (0000h).
3.
Calculate the time to the falling edge of the pulse
based on the desired pulse width and the time to
the rising edge of the pulse.
based on the desired pulse width and the time to
the rising edge of the pulse.
4.
Write the values computed in Steps 2 and 3
above into the Output Compare 1 register,
OC1R, and the Output Compare 1 Secondary
register, OC1RS, respectively.
above into the Output Compare 1 register,
OC1R, and the Output Compare 1 Secondary
register, OC1RS, respectively.
5.
Set Timer Period register, PRy, to value equal to
or greater than the value in OC1RS, the Output
Compare 1 Secondary register.
or greater than the value in OC1RS, the Output
Compare 1 Secondary register.
6.
Set the OCM bits to ‘100’ and the OCTSEL
(OC1CON<3>) bit to the desired timer source.
The OC1 pin state will now be driven low.
(OC1CON<3>) bit to the desired timer source.
The OC1 pin state will now be driven low.
7.
Set the TON (TyCON<15>) bit to ‘1’, which
enables the compare time base to count.
enables the compare time base to count.
8.
Upon the first match between TMRy and OC1R,
the OC1 pin will be driven high.
the OC1 pin will be driven high.
9.
When the incrementing timer, TMRy, matches
the Output Compare 1 Secondary register,
OC1RS, the second and trailing edge
(high-to-low) of the pulse is driven onto the OC1
pin. No additional pulses are driven onto the
OC1 pin and it remains low. As a result of the
second compare match event, the OC1IF inter-
rupt flag bit is set, which will result in an interrupt
if it is enabled, by setting the OC1IE bit. For
further information on peripheral interrupts, refer
to
the Output Compare 1 Secondary register,
OC1RS, the second and trailing edge
(high-to-low) of the pulse is driven onto the OC1
pin. No additional pulses are driven onto the
OC1 pin and it remains low. As a result of the
second compare match event, the OC1IF inter-
rupt flag bit is set, which will result in an interrupt
if it is enabled, by setting the OC1IE bit. For
further information on peripheral interrupts, refer
to
10. To initiate another single pulse output, change
the Timer and Compare register settings, if
needed, and then issue a write to set the OCM
bits to ‘100’. Disabling and re-enabling of the
timer and clearing the TMRy register are not
required, but may be advantageous for defining
a pulse from a known event time boundary.
needed, and then issue a write to set the OCM
bits to ‘100’. Disabling and re-enabling of the
timer and clearing the TMRy register are not
required, but may be advantageous for defining
a pulse from a known event time boundary.
The output compare module does not have to be
disabled after the falling edge of the output pulse.
Another pulse can be initiated by rewriting the value of
the OC1CON register.
disabled after the falling edge of the output pulse.
Another pulse can be initiated by rewriting the value of
the OC1CON register.
15.2
Setup for Continuous Output
Pulse Generation
Pulse Generation
When the OCM control bits (OC1CON<2:0>) are set to
‘101’, the selected output compare channel initializes
the OC1 pin to the low state and generates output
pulses on each and every compare match event.
For the user to configure the module for the generation
of a continuous stream of output pulses, the following
steps are required (these steps assume the timer
source is initially turned off, but this is not a requirement
for the module operation):
1.
‘101’, the selected output compare channel initializes
the OC1 pin to the low state and generates output
pulses on each and every compare match event.
For the user to configure the module for the generation
of a continuous stream of output pulses, the following
steps are required (these steps assume the timer
source is initially turned off, but this is not a requirement
for the module operation):
1.
Determine the instruction clock cycle time. Take
into account the frequency of the external clock
to the timer source (if one is used) and the timer
prescaler settings.
into account the frequency of the external clock
to the timer source (if one is used) and the timer
prescaler settings.
2.
Calculate time to the rising edge of the output
pulse relative to the TMRy start value (0000h).
pulse relative to the TMRy start value (0000h).
3.
Calculate the time to the falling edge of the pulse
based on the desired pulse width and the time to
the rising edge of the pulse.
based on the desired pulse width and the time to
the rising edge of the pulse.
4.
Write the values computed in Step 2 and 3 above
into the Output Compare 1 register, OC1R, and the
Output Compare 1 Secondary register, OC1RS,
respectively.
into the Output Compare 1 register, OC1R, and the
Output Compare 1 Secondary register, OC1RS,
respectively.
5.
Set the Timer Period register, PRy, to a value
equal to or greater than the value in OC1RS.
equal to or greater than the value in OC1RS.
6.
Set the OCM bits to ‘101’ and the OCTSEL bit to
the desired timer source. The OC1 pin state will
now be driven low.
the desired timer source. The OC1 pin state will
now be driven low.
7.
Enable the compare time base by setting the
TON (TyCON<15>) bit to ‘1’.
TON (TyCON<15>) bit to ‘1’.
8.
Upon the first match between TMRy and OC1R,
the OC1 pin will be driven high.
the OC1 pin will be driven high.
9.
When the compare time base, TMRy, matches the
OC1RS, the second and trailing edge (high-to-low)
of the pulse is driven onto the OC1 pin.
OC1RS, the second and trailing edge (high-to-low)
of the pulse is driven onto the OC1 pin.
10. As a result of the second compare match event,
the OC1IF interrupt flag bit is set.
11. When the compare time base and the value in its
respective Timer Period register match, the TMRy
register resets to 0x0000 and resumes counting.
register resets to 0x0000 and resumes counting.
12. Steps 8 through 11 are repeated and a continu-
ous stream of pulses is generated indefinitely.
The OC1IF flag is set on each OC1RS/TMRy
compare match event.
The OC1IF flag is set on each OC1RS/TMRy
compare match event.
Note:
This data sheet summarizes the features
of this group of PIC24F devices. It is not
intended to be a comprehensive refer-
ence source. For more information on
Output Compare, refer to the “PIC24F
Family Reference Manual”
of this group of PIC24F devices. It is not
intended to be a comprehensive refer-
ence source. For more information on
Output Compare, refer to the “PIC24F
Family Reference Manual”
, Section 16.
“Output Compare”
(DS39706).