FUJITSU Semiconductor Controller MB89950/950A - Manual (Page 121)

107
CHAPTER 5 TIMEBASE TIMER
5.5 Operation of Timebase Timer
The timebase timer has the interval timer function and the clock supply function for
some peripherals.
■ Operation of interval timer function (timebase timer)
Figure 5.5-1 "Interval timer function settings" shows the settings required to operate the interval timer
function.
Figure 5.5-1 Interval timer function settings
Provided that the main clock is oscillating, the timebase timer counter continues to count up in synchronous
with the internal count clock (divide-by-two main clock oscillation frequency).
After being cleared (TBR = "0"), the counter restarts to count up from zero. The timebase timer sets the
overflow interrupt request flag bit (TBIF) to "1" when an overflow occurs on the interval timer bit.
Consequently, the timebase timer generates interrupt requests at fixed intervals (the selected interval time),
based on the time that the counter is cleared.
■ Operation of clock supply function
The timebase timer is also used as a timer to generate the main clock oscillation stabilization delay time.
The time from when the timebase timer counter is cleared and starts counting up until an overflow occurs
on the oscillation stabilization delay time bit is the oscillation stabilization delay time.
If the timebase timer output is selected by the watchdog timer counter (WDTC: WTE3 to WTE0 =
"0101
B
"), clearing the timebase timer counter by entering to stop mode (STBC: STP = "1") will also clear
the watchdog timer at the same time.
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
TBTC TBIF TBIE TBR TBC1 TBC0
0 1 0
: Used bit
1 : Set “1”
0 : Set “0”