Rev. 1.00
116
September 11, 2018
Rev. 1.00
117
September 11, 2018
HT45F4050
A/D NFC Flash MCU
HT45F4050
A/D NFC Flash MCU
Capture Input Mode
To select this mode bits PTM1 and PTM0 in the PTMC1 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 PTPI or PTCK pin, selected by the PTCAPTS bit in the PTMC1 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 PTIO1 and PTIO0 bits in the PTMC1 register. The counter
is started when the PTON bit changes from low to high which is initiated using the application
program.
When the required edge transition appears on the PTPI or PTCK pin the present value in the counter
will be latched into the CCRA registers and a PTM interrupt generated. Irrespective of what events
occur on the PTPI or PTCK pin the counter will continue to free run until the PTON 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 PTM 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 PTIO1 and PTIO0 bits can select the active trigger edge on the PTPI or PTCK pin to be a rising
edge, falling edge or both edge types. If the PTIO1 and PTIO0 bits are both set high, then no capture
operation will take place irrespective of what happens on the PTPI or PTCK pin, however it must be
noted that the counter will continue to run.
As the PTPI or PTCK 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 PTCCLR, PTOC and PTPOL bits are not
used in this mode.