Rev. 1.50
114
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Rev. 1.50
115
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HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
Capture Input Mode
To select this mode bits TnM1 and TnM0 in the TMnC1 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 TPn or TCKn pin, selected by the TnCAPTS bit in the TMnC1 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 TnIO1 and TnIO0 bits in the TMnC1 register. The counter
is started when the TnON bit changes from low to high which is initiated using the application
program.
When the required edge transition appears on the TPn or TCKn pin the present value in the counter
will be latched into the CCRA registers and a TMn interrupt generated. Irrespective of what events
occur on the TPn or TCKn pin the counter will continue to free run until the TnON 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 TMn 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 TnIO1
and TnIO0 bits can select the active trigger edge on the TPn or TCKn pin to be a rising edge, falling
edge or both edge types. If the TnIO1 and TnIO0 bits are both set high, then no capture operation
will take place irrespective of what happens on the TPn or TCKn pin, however it must be noted that
the counter will continue to run.
As the TPn or TCKn pin is pin shared with other functions, care must be taken if the TMn is in the
Input Capture 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 TnCCLR, TnOC and TnPOL bits are not
used in this Mode.