Rev. 1.00
102
September 11, 2018
Rev. 1.00
103
September 11, 2018
HT45F4050
A/D NFC Flash MCU
HT45F4050
A/D NFC Flash MCU
Capture Input Mode
To select this mode bits STM1 and STM0 in the STMC1 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 STPI pin, whose active edge can be a rising edge, a falling edge or both rising
and falling edges; the active edge transition type is selected using the STIO1 and STIO0 bits in
the STMC1 register. The counter is started when the STON bit changes from low to high which is
initiated using the application program.
When the required edge transition appears on the STPI pin the present value in the counter will be
latched into the CCRA registers and a STM interrupt generated. Irrespective of what events occur
on the STPI pin the counter will continue to free run until the STON 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 STM 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 STIO1
and STIO0 bits can select the active trigger edge on the STPI pin to be a rising edge, falling edge or
both edge types. If the STIO1 and STIO0 bits are both set high, then no capture operation will take
place irrespective of what happens on the STPI pin, however it must be noted that the counter will
continue to run. The STCCLR and STDPX bits are not used in this mode.