Figure 5.6 Effect On Buzzer Output Of Clearing Timebase Timer - Fujitsu F2MC-8L MB89620 Series Hardware Manual

6
5. Notes on Using Timebase Timer
This section lists points to note when using the timebase timer.
n Notes on Using Timebase Timer
l Notes on setting bits by program
The system cannot recover from interrupt processing if the overflow interrupt request flag bit
(TBTC: TBOF) is "1" and the interrupt request enable bit is enabled (TBTC: TBIE = "1"). Always
clear the TBOF bit.
Clearing timebase timer
l
In addition to being cleared by the timebase timer initialization bit (TBTC: TBR = "0"), the timer
is cleared whenever the oscillation stabilization delay time is required. Clearing the timebase
timer also clears the watchdog timer.
Using as timer for oscillation stabilization delay time
l
As the source oscillation is stopped when the power is turned on and during stop mode, the
timebase timer provides the oscillation stabilization delay time after the oscillator starts.
An appropriate oscillation stabilization delay time must be selected for the type of resonator
connected to the oscillator (clock generator). The oscillation stabilization delay time should be
used as a guideline since the oscillation cycle is unstable immediately after oscillation starts.
Reference: See Section 3.6.3, "Oscillation Stabilization Delay Time" for details.
l Notes on peripheral functions that provide a clock supply from timebase timer
As the clock derived from the timebase timer restarts output from its initial state when the
timebase timer counter is cleared, the "H" level may be shorter or the "L" level longer by a
maximum of half cycle. The clock of the watchdog timer also restarts output from its initial state.
However, as the watchdog timer counter is cleared at the same time, the watchdog timer
operates in normal cycle.
Figure 5.6 shows the effect on the buzzer output of clearing the timebase timer.
For the case when the buzzer selection bits in the buzzer register (BZCR: BZ1, BZ0) are set to "01".
(Divide-by-8192 source oscillation, approximately 1.221 kHz output at 10 MHz operation)
126
CHAPTER 5 TIMEBASE TIMER
Counter value
00FFF
H
00800
H
00000
H
Clock supplied to
the buzzer output

Figure 5.6 Effect on Buzzer Output of Clearing Timebase Timer

Clearing the counter by the program (TBTC: TBR = "0")
MB89620 series