Nxp semiconductors – NXP Semiconductors P89LPC9321 UM10310 User Manual
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UM10310
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NXP Semiconductors
UM10310
P89LPC9321 User manual
Two bits in OCCRx, the Output Compare x Mode bits OCMx1 and OCMx0 select what
action is taken when a compare match occurs. Enabled compare actions take place even
if the interrupt is disabled.
In order for a Compare Output Action to occur, the compare values must be within the
counting range of the CCU timer.
When the compare channel is enabled, the I/O pin (which must be configured as an
output) will be connected to an internal latch controlled by the compare logic. The value of
this latch is zero from reset and can be changed by invoking a forced compare. A forced
compare is generated by writing a logic 1 to the Force Compare x Output bit - FCOx bit in
OCCRx. Writing a one to this bit generates a transition on the corresponding I/O pin as set
up by OCMx1/OCMx0 without causing an interrupt. In basic timer operating mode the
FCOx bits always read zero. (Note: This bit has a different function in PWM mode.) When
an output compare pin is enabled and connected to the compare latch, the state of the
compare pin remains unchanged until a compare event or forced compare occurs.
When the user writes to change the output compare value, the values written to OCRH2x
and OCRL2x are transferred to two 8-bit shadow registers. In order to latch the contents
of the shadow registers into the capture compare register, the user must write a logic 1 to
the CCU Timer Compare/Overflow Update bit TCOU2, in the CCU Control Register 1 -
TCR21. The function of this bit depends on whether the timer is running in PWM mode or
in basic timer mode. In basic timer mode, writing a one to TCOU2 will cause the values to
be latched immediately and the value of TCOU2 will always read as zero. In PWM mode,
writing a one to TCOU2 will cause the contents of the shadow registers to be updated on
the next CCU Timer overflow. As long as the latch is pending, TCOU2 will read as one and
will return to zero when the latch takes place. TCOU2 also controls the latching of all the
Output Compare registers as well as the Timer Overflow Reload registers - TOR2.
Table 39.
Capture compare control register (CCRx - address Exh) bit allocation
Bit
7
6
5
4
3
2
1
0
Symbol
ICECx2
ICECx1
ICECx0
ICESx
ICNFx
FCOx
OCMx1
OCMx0
Reset
0
0
0
0
0
0
0
0
Table 40.
Capture compare control register (CCRx - address Exh) bit description
Bit Symbol
Description
0
OCMx0
Output Compare x Mode. See
Table 42 “Output compare pin behavior.”
1
OCMx1
2
FCOx
Force Compare X Output Bit. When set, invoke a force compare.
3
ICNFx
Input Capture x Noise Filter Enable Bit. When logic 1, the capture logic needs to see four consecutive
samples of the same value in order to recognize an edge as a capture event. The inputs are sampled
every two CCLK periods regardless of the speed of the timer.
4
ICESx
Input Capture x Edge Select Bit. When logic 0: Negative edge triggers a capture, When logic 1: Positive
edge triggers a capture.
5
ICECx0
Capture Delay Setting Bit 0. See
for details.
6
ICECx1
Capture Delay Setting Bit 1. See
for details.
7
ICECx2
Capture Delay Setting Bit 2. See
for details.