Fujitsu F2MC-8L MB89620 Series Hardware Manual page 139

1
5. Overview of Timebase Timer
The timebase timer provides interval timer functions. Four different interval times can
be selected. The timebase timer uses a 20-bit free-run counter which counts-up in
sync with the internal count clock (divide-by-two source oscillation).
The timebase timer also provides the timer output for the oscillation stabilization delay
time and the operating clock for the watchdog and other timers.
n Interval Timer Function
The interval timer function generates repeated interrupts at fixed time intervals.
• The timer generates an interrupt each time the interval timer bit overflows on the timebase
timer counter.
• The interval timer bit (interval time) can be selected from four different settings.
Table 5.1a lists the available interval times for the timebase timer.
Table 5.1a Timebase Timer Interval Time
Internal count clock cycle
F : Source oscillation
C
The values enclosed in parentheses ( ) are for a 10 MHz source oscillation.
n Clock Supply Function
The clock supply function provides the timer output used for the oscillation stabilization delay
time (can select one of two values as an option) and an operation clock for some peripheral
functions.
Table 5.1b lists the cycles of the clocks that the timebase timer supplies to various peripherals.
Table 5.1b Clock Supplied by Timebase Timer
Clock destination
Oscillation stabilization
delay time (optional)
Watchdog timer
Buzzer output
A/D converter
F : Source oscillation
C
The values enclosed in parentheses ( ) are for a 10 MHz source oscillation.
Note: The oscillation stabilization delay time should be used as a guideline since the oscillation cycle is
unstable immediately after oscillation starts.
118
CHAPTER 5 TIMEBASE TIMER
(0.2 µs)
2/F
C
2 18 /F
2 14 /F
21
2 /F
C
2 11 /F to 2
C
ms)
2
Interval time
2 15 /F (approx. 3.3 ms)
C
2 17 /F (approx. 13.1 ms)
C
2 19 /F (approx. 52.4 ms)
C
2 21 /F (approx. 209.7 ms)
C
Clock cycle
Oscillation stabilization delay time for a crystal
(approx. 26.2 ms)
C
resonator
Oscillation stabilization delay time for a ceramic
(approx. 1.64 ms)
C
resonator
(approx. 209.7 ms) Count-up clock for the watchdog timer
13 /F (approx. 0.2 to 0.8
C
See Chapter 11, "Buzzer Output."
(102.4 µs)
Clock for continuous activation
8 /F
C
Remarks
MB89620 series