CT-161-CD Fujitsu Semiconductor America Inc, CT-161-CD Datasheet - Page 75

• Manufacturer Part Number: CT-161-CD
• Description: KIT 16LX FOR MB90F387
• Manufacturer: Fujitsu Semiconductor America Inc
• Series: F²MC-16LXr
• Type: MCUr

Specifications of CT-161-CD

• Contents: Board, Cable, CD
• For Use With/related Products: MB90F387S
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 865-1103

6 “Let's blink the LED by using a timer interrupt.”
© Fujitsu
The procedure for controlling the LED blinking is described in Item 2.5 in Chapter2. There are
some other methods to control the LED blinking other than the method described in Chapter 2.
One of them is the method using a "timer interrupt." This chapter describes the method to control
the LED blinking by using a 16-bit reload timer.
6.1
Let's begin with a brief explanation of the "timer." The word "timer" is often heard in daily
life, such as a recording timer of VCR, a start timer or sleep timer of the audio system, a
kitchen timer for cooking, or the timer function of an alarm clock. The function of the timer
contained in the microcomputer is the same as those timers. Let's take the alarm clock timer
as an example to explain the timer function. Most of the people set the alarm clock timer for
a certain time and wake up at the sound of the alarm every morning. What would happen if
there was no alarm timer function? People would be bothered about the time to wake up
once the dawn breaks and could not keep relaxing and sleeping. People can re-realize that
the timer function of the alarm clock allows us to sleep tight until the time to get up.
The microcomputer has the timer interrupt function that performs as an alarm timer function.
In this case, the timer interrupt is used for the LED-on time count and the LED-off time count.
Because the LED blinking control described in Item 2.5 in Chapter2 counts the LED-on time
and LED-off time by executing the CPU instruction, the CPU is always required to perform
the processing for controlling the LED blinking. Figure 6-1 LED blinking processing
without using the timer interrupt shows the LED blinking processing without using the
timer interrupt. This figure shows that the CPU must always control the LED and there is no
time for other processing.
time that is described in Figure 6-1 so that the CPU does not have to count the LED-on and
-off time. The CPU can perform processing other than the LED blinking control accordingly.
When a timer is used, the timer can take the processing of counting the LED-on and -off
What is a timer?
CPU processing
Figure 6-1 LED blinking processing without using the timer interrupt
ON/OFF switching
LED-on time count
LED-on
-
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ON/OFF switching
LED-off time count
LED-off
ON/OFF switching
LED-on time count
LED-on
LED-off