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CHAPTER 5 TIME-BASE TIMER

5.2 Configuration of Time-base Timer

The time-base timer consists of the following four function blocks.

Time-base counter

Counter clear circuit

Interval timer selector

Time-base timer control register (TBTC)

Block Diagram of Time-base Timer

Figure 5.2-1 Block Diagram of Time-base Timer

Time-base timer counter

A 21-bit up counter that accepts the oscillation frequency divided by two as the count clock and stops

operating when oscillation stops.

Counter clear circuit

Clears the counter when the TBTC register is set (TBR = 0), stop mode is entered (STBC: STP = 1), or a

power-on reset occurs.

Interval timer selector

Selects 1 bit for the interval timer from four bits in the time-base counter. When the specified bit overflows,

an interrupt occurs.

Time-base timer control register (TBTC)

Selects a time interval, clears the counter, controls interrupts, or checks the status.

TB0F TBIE TBC1 TBC0 TBR
OF
OF
OF
OF
F
CH
: Oscillation frequency
X2
1
Time-base timer counter
X2
2
X2
3
X2
6
X2
7
X2
8
X2
9
X2
10
X2
11
X2
12
X2
13
X2
14
X2
15
X2
16
X2
17
X2
20
X2
21
To A/D converter To watchdog timer
F
CH
divided
by two
Clearing counter To clock control
section oscillation
stabilization time
selector
Clearing watchdog timer
Power-on reset
Starting stop mode
(in normal mode)
Counter
clear
circuit
Interval timer
selector
IRQ7 (time-base timer interrupt)
OF: Overflow
Time-base timer control register (TBTC)