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CHAPTER 5 TIME-BASE TIMER
5.5 Operations of Time-base Timer Functions
The time-base timer functions as an interval timer or supplies clocks to some
peripherals.
■ Operations of Interval Timer Function (Time-base Timer)
To use as an interval timer, the settings shown below must be made.
Figure 5.5-1 Setting Interval Timer Function
The counter in the time-base timer continues to count up in synchronization with the internal count clock
(at the oscillation frequency divided by two) as long as the clock oscillates.
The counter counts from "0" upon being cleared (TBR = 0). When the interval timer bit overflows, the
overflow interrupt request flag bit (TBOF) is set to "1". In other words, interrupts are generated at specified
intervals, starting from when the counter is cleared.
■
Operations of Clock Supply Function
The time-base timer is often used to make oscillation stabilization wait time. The oscillation stabilization
time is measured from when the time-base timer counter is cleared to when the oscillation stabilization bit
overflows. One of three oscillation stabilization time can be selected by the oscillation stabilization time
selection bits of the system clock control register (SYCC: WT1, WT0).
The time-base timer supplies clocks to the watchdog timer and A/D converter. Clearing the time-base timer
counter affects the operation of continuous activation cycles. In addition, when the time-base timer is
cleared, the counter in the watchdog timer is also cleared.
■
Operations of Time-base Timer
Figure 5.5-2 shows the operation of the time-base timer when:
• power-on reset occurs.
• sleep mode is entered while the interval timer function is being performed in normal mode.
• stop mode is entered.
• a counter clear request is generated.
In stop mode, the time-base timer is cleared and stops operating. When returning from stop mode, the time-
base timer counts the oscillation stabilization time.
bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
TBTC
TBOF
TBIE
TBC1
TBC0
TBR
0
1
0
1
0
: Used bit
: Set to "1"
: Set to "0"