Rev. 2.10
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Rev. 2.10
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HT68F20/HT68F30/HT68F40/HT68F50/HT68F60
HT68FU30/HT68FU40/HT68FU50/HT68FU60
Enhanced I/O Flash Type 8-Bit MCU with EEPROM
HT68F20/HT68F30/HT68F40/HT68F50/HT68F60
HT68FU30/HT68FU40/HT68FU50/HT68FU60
Enhanced I/O Flash Type 8-Bit 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_0 or TPn_1 pin, whose 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_0 or TPn_1 pin the present value in the
counter will be latched into the CCRA registers and a TM interrupt generated. Irrespective of what
events occur on the TPn_0 or TPn_1 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 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 TnIO1 and TnIO0 bits can select the active trigger edge on the TPn_0 or TPn_1
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_0 or TPn_1
pin, however it must be noted that the counter will continue to run.
As the TPn_0 or TPn_1 pin is pin shared with other functions, care must be taken if the TM 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 and TnDPX bits are not used in
this Mode.