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CHAPTER 7 16-bit I/O timer
7.1
Overview of 16-bit Input/Output Timer
The 16-bit input/output timer is a combined module that consists of a 16-bit free-run
timer (x 1 unit) and an input capture (x 2 units/4 input pins).The clock cycle of an input
signal and a pulse width can be measured based on the 16-bit input/output timer.
I Configuration of 16-bit Input/Output Timer
The 16-bit input/output timer consists of the following modules:
• 16-bit free-run timer (x 1 unit)
• Input capture (x 2 units with 2 input pins each)
I Functions of 16-bit Input/Output Timer
G
Functions of 16-bit free-run timer
The 16-bit free-run timer consists of a 16-bit up counter, a timer counter control status register, and a
prescaler.The 16-bit up counter increments in synchronization with the division ratio of the machine clock.
• Count clock is selected from four machine clock division ratios.Count Clock: φ , φ /2, φ /4, φ /8, φ /16,
φ /32, φ /64, φ /128
• An overflow in the count value generates an interrupt.
• Interrupt generation starts the extended intelligent I/O service (EI
• Either a reset or software reset by the timer count clear bit TCCS: CLR) clears the count value of the 16-
bit free-run timer to "0000
• The count value of the 16-bit free-run timer is output to the input capture and can be used as the base
time for capture operation.
G
Functions of input capture
When the input capture detects the edge of the external signal input to the input pins, it stores the count
value of the 16-bit free-run timer in the input capture data registers. The input capture consists of the input
capture data registers corresponding to four input pins, an input capture control status register, and an edge
detection circuit.
• The detected edge can be selected from among the rising edge, falling edge, and both edges.
• Detecting the edge of the input signal generates an interrupt request to the CPU.
• Interrupt generation starts the extended intelligent I/O service (EI
• The input capture unit has four sets of input pins and input capture data registers which can be used to
measure up to four events.
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