MB90480/485 Series
15. Timebase Timer
The timebase timer is an 18-bit free run counter (timebase counter) that counts up in synchronization with the
internal count clock signal (base oscillator × 2) , and functions as an interval timer with a choice of four types of
time intervals. Other functions provided by this module include timer output for the oscillator stabilization wait
period, and operating clock signal feed for other timer circuits such as the watchdog timer.
(1) Register List
Timebase timer control register (TBTC)
15
14
13
12
11
10
9
8
0000A9H
RESV
⎯
⎯
TBIE
TBOF
TBR
TBC1
TBC0
Read/write
Initial value
R/W
1
⎯
X
⎯
X
R/W
0
R/W
0
W
1
R/W
0
R/W
0
(2) Block Diagram
To PPG timer
To watchdog
timer
Timebase
timer counter
HCLK × 2
× 21 × 22
× 28 × 29 × 210 × 211 × 212 × 213 × 214 × 215 × 216 × 217 × 218
OF
OF
OF
OF
Power-on reset
Stop mode start
To clock control
module oscillator
stabilization wait
time selector
Counter
clear
control
circuit
Hold status start
CKSCR : MCS = 1→0*1
CKSCR : SCS = 0→1*2
Interval timer
selector
TBOF
set
TBOF clear
⎯
⎯
Timebase timer control register (TBTC)
Timebase timer interrupt signal
RESV
TBIE TBOF TBR TBC1 TBC0
OF
: Overflow
HCLK : Oscillator clock
*1
*2
: Switch machine clock from main clock or sub clock to PLL clock.
: Switch machine clock from sub clock to main clock.
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