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CHAPTER 8 8-BIT TIMER 1 TM1
8.4 8-Bit Timer 1 Operations
8.4.1 8-bit interval timer operation
The 8-bit timer 1 operates as an interval timer which generates interrupt requests repeatedly at intervals of the
count value preset to 8-bit compare register 1 (CR1).
When the count values of the 8-bit counter 1 (TM1) match the values set to CR1, counting continues with the TM1
values cleared to 0 and the interrupt request signal (INTTM1) is generated.
Count clock of the TM1 can be selected with bits 0 to 2 (TCL10 to TCL12) of the timer clock select register 1 (TCL1).
[Setting]
<1>
Set the registers.
• TCL1 : Select count clock.
• CR1 : Compare value
<2>
After TCE1 = 1 is set, count operation starts.
<3>
If the values of TM1 and CR1 match, the INTTM1 is generated and TM1 is cleared to 00H.
<4>
INTTM1 generates repeatedly at the same interval. Set TCE1 to 0 to stop count operation.
Figure 8-4. Interval Timer Operation Timings (1/3)
(a) Basic operation
t
Count clock
TM1 count value
CR1
TCE1
INTTM1
TM1 interval time
Note
Start count
Clear
Clear
00H
01H
N
00H
01H
N
00H
01H
N
N
N
N
N
Interrupt received
Interrupt received
Interval time
Interval time
Interval time
Remark
Interval time = (N + 1)
×
t: N = 00H to FFH
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