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Rev. 1.71
94
April 11, 2017
Rev. 1.71
95
April 11, 2017
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
Capture Input Mode
To select this mode bits PTnM1 and PTnM0 in the PTMnC1 register should be set to 01 respectively.
This mode enables external signals to capture and store the present value of the internal counter
and can therefore be used for applications such as pulse width measurements. The external signal
is supplied on the PTPnI or PTCKn pin, selected by the PTnCKS bit in the PTMnC1 register. The
input pin active edge can be either a rising edge, a falling edge or both rising and falling edges; the
active edge transition type is selected using the PTnIO1 and PTnIO0 bits in the PTMnC1 register.
The counter is started when the PTnON bit changes from low to high which is initiated using the
application program.
When the required edge transition appears on the PTPnI or PTCKn pin the present value in the
counter will be latched into the CCRA register and a TM interrupt generated. Irrespective of what
events occur on the PTPnI or PTCKn pin the counter will continue to free run until the PTnON bit
changes from high to low. When a CCRP compare match occurs the counter will reset back to zero;
in this way the CCRP value can be used to control the maximum counter value. When a CCRP
compare match occurs from Comparator P, a TM interrupt will also be generated. Counting the
number of overflow interrupt signals from the CCRP can be a useful method in measuring long pulse
widths. The PTnIO1 and PTnIO0 bits can select the active trigger edge on the PTPnI or PTCKn pin
to be a rising edge, falling edge or both edge types. If the PTnIO1 and PTnIO0 bits are both set high,
then no capture operation will take place irrespective of what happens on the PTPnI or PTCKn pin,
however it must be noted that the counter will continue to run.
As the PTPnI or PTCKn pin is pin shared with other functions, care must be taken if the PTM is in
the Capture Input Mode. This is because if the pin is setup as an output, then any transitions on this
pin may cause an input capture operation to be executed. The PTnCCLR, PTnOC and PTnPOL bits
are not used in this Mode.