Setup Example - Panasonic MN101L Series User Manual

Chapter 8
8-bit Timer
8.7.2

Setup Example

Setup Example of Simple Pulse Width Measurement by 8-bit Timer
Here is an example that Timer 0 measures "Low" pulse width of the input signal of IRQ0.
SYSCLK/2 is selected as a clock source for Timer 0.
The setup procedure and the description of each step are shown below.
Step
1 Disable the timer counter
Set the timer mode register
2
3
Set the prescaler
4
Set the compare register
5
6 Set the interrupt level
7 Set the interrupt valid edge
8 Enable the interrupt
9 Enable the timer counter
The internal enable is set while the sampled signal at the count clock, which is External Interrupt 0 (IRQ0) input,
is "Low" level.
TM0BC starts counting up from "0x00" after the internal enable is set. Timer 0 continues counting up while IRQ0
is "Low", and stops counting up when the sampled signal of IRQ0 becomes "High" level. At the same time,
"Low" period of IRQ0 input can be detected by reading the value of TM0BC in the interrupt process.
VIII - 30 Simple Pulse Width Measurement
Setting
TM0MD.TM0EN = 0
TM0MD.TM0PWM = 0
TM0MD.TM0MOD = 1
TM0MD.TM0CK1-0 = 01
CK0MD.TM0PSC1-0 = X0
CK0MD.TM0BAS = 1
TM0OC = 0xFF
TM0ICR.TM0LV1-0
IRQ0ICR.REDG0 = 1
TM0ICR.TM0IE = 1
TM0MD.TM0EN = 1
Register
Disable the timer count operation.
Select the pulse width measurement function.
Select the prescaler as the clock source.
Select SYSCLK/2.
Set the value larger than that of the "Low" period of measured
pulse width.
Refer to [3.1.3 Maskable Interrupt Control Register Setup].
Set the external interrupt valid edge.
Enable the external interrupt.
Enable the timer count operation.
Description