287
12.4 Operation of 16-Bit Reload Timer
12.4 Operation of 16-Bit Reload Timer
The 16-bit reload timer performs the following two types of operation:
• Internal clock operation
• Underflow operation
■
Internal Clock Operation
When a frequency division clock of the internal clock is used to run the timer, a machine clock
frequency divided by 2, 8, or 32 can be selected as the clock source.
To make the counter start counting immediately when counting is enabled, set both the CNTE
and TRG bits of the control status register to "1". The trigger input by the TRG bit is always
effective, regardless of the operation mode, when the timer is active (CNTE = "1").
Figure 12.4-1 is a counter start and operation timing chart.
Time T (peripheral clock machine cycle) is required from when a counter start trigger is input to
when the reload register data is loaded to the counter.
Figure 12.4-1 Counter Start and Operation Timing
■
Underflow Operation
An underflow occurs when the counter value changes from 0000
H
to FFFF
H
. That is, an
underflow occurs at a count of "reload register value + 1."
If the RELD bit of the control register is "1" when an underflow occurs, the value in the reload
register is loaded to the counter and the counter continues counting. When the RELD bit is "0",
the counter stops at FFFF
H
.
When an underflow occurs, the UF bit of the control register is set, and an interrupt request is
issued when the INTE bit is "1".
Figure 12.4-2 is a timing chart for underflow operation timing.
T
- 1
- 1
- 1
Count clock
Counter
Data loading
CNTE (register)
TRG (register)
Reload data
Summary of Contents for MB91F109
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Page 3: ...FUJITSU LIMITED FR30 32 Bit Microcontroller MB91F109 Hardware Manual ...
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Page 10: ...vi ...
Page 24: ...xx ...
Page 96: ...72 CHAPTER 2 CPU ...
Page 224: ...200 CHAPTER 4 BUS INTERFACE ...
Page 234: ...210 CHAPTER 5 I O PORTS ...
Page 268: ...244 CHAPTER 9 U TIMER ...
Page 290: ...266 CHAPTER 10 UART ...
Page 314: ...290 CHAPTER 12 16 BIT RELOAD TIMER ...
Page 322: ...298 CHAPTER 13 BIT SEARCH MODULE ...
Page 392: ...368 CHAPTER 16 FLASH MEMORY ...
Page 432: ...408 APPENDIX E Instructions F Table E 2 Instruction Formats OP rel11 5 11 ...
Page 448: ...424 APPENDIX E Instructions ...
Page 449: ...425 INDEX INDEX The index follows on the next page This is listed in alphabetic order ...
Page 458: ...434 INDEX ...
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Page 461: ...FUJITSU SEMICONDUCTOR FR30 32 Bit Microcontroller MB91F109 Hardware Manual ...