200
CHAPTER 13 WATCH PRESCALER
13.5
Explanation of Watch Prescaler Operations and Setup
Procedure Example
The watch prescaler operates as an interval timer.
■
Operations of Interval Timer Function (Watch Prescaler)
The counter of the watch prescaler continues to count down using the subclock divided by two as its count
clock as long as the subclock oscillates.
When cleared (WPCR:WCLR = 1), the counter starts to count down from "7FFF
H
". Once "0000
H
" is
reached, the counter returns to "7FFF
H
" to continue the count. When the time set by the interrupt interval
time select bits is reached during down-counting, the watch interrupt request flag bit (WPCR:WTIF) is set
to "1" in any mode other than the main stop mode. In other words, a watch interrupt request is generated at
each selected interval time, based on the time when the counter was last cleared.
■
Clearing Watch Prescaler
If the watch prescaler is cleared when the output of the watch prescaler is used in other peripheral
functions, this will affect the operation by changing the count time or in other manners.
When clearing the counter by using the watch prescaler initialization bit (WTCR:WCLR), perform setup so
that this does not have unexpected effects on other peripheral functions.
When the output of the watch prescaler is selected as the count clock, clearing the watch prescaler also
clears the watchdog timer.
The watch prescaler is cleared not only by the watch prescaler initialization bit (WTCR:WCLR) but also
when the subclock is stopped and a count is required for the oscillation stabilization wait time.
•
When moving from the subclock mode or sub PLL clock mode to the stop mode
•
When the subclock oscillation stop bit in the system clock control register (SYCC:SUBS) is set to "1" in
the main clock mode or main PLL clock mode
In addition, the counter of the watch prescaler is cleared and stops operation when a reset is generated.
■
Operating Examples of Watch Prescaler
Figure 13.5-1 shows operating examples under the following conditions:
1) When a power-on reset is generated
2) When entering the sleep mode during the operation of the interval timer function in the subclock mode
or sub PLL clock mode
3) When entering the stop mode during the operation of the interval timer function in the subclock mode or
sub PLL clock mode
4) When a request is issued to clear the counter
The same operation is performed when changing to the watch mode as for when changing to the sleep
mode.
Summary of Contents for F2 MC-8FX Family
Page 2: ......
Page 4: ......
Page 34: ...20 CHAPTER 1 DESCRIPTION ...
Page 38: ...24 CHAPTER 2 HANDLING DEVICES ...
Page 39: ...25 CHAPTER 3 MEMORY SPACE This chapter describes memory space 3 1 Memory Space 3 2 Memory Map ...
Page 56: ...42 CHAPTER 5 CPU ...
Page 73: ...59 CHAPTER 6 CLOCK CONTROLLER ...
Page 96: ...82 CHAPTER 6 CLOCK CONTROLLER ...
Page 104: ...90 CHAPTER 7 RESET ...
Page 105: ...91 CHAPTER 8 INTERRUPTS This chapter explains the interrupts 8 1 Interrupts ...
Page 174: ...160 CHAPTER 10 TIMEBASE TIMER ...
Page 184: ...170 CHAPTER 10 TIMEBASE TIMER ...
Page 218: ...204 CHAPTER 13 WATCH PRESCALER ...
Page 257: ...243 CHAPTER 16 8 16 BIT COMPOSITE TIMER ...
Page 261: ...247 CHAPTER 16 8 16 BIT COMPOSITE TIMER ...
Page 288: ...274 CHAPTER 16 8 16 BIT COMPOSITE TIMER ...
Page 301: ...287 CHAPTER 17 16 BIT PPG TIMER ...
Page 316: ...302 CHAPTER 17 16 BIT PPG TIMER ...
Page 382: ...368 CHAPTER 21 UART SIO DEDICATED BAUD RATE GENERATOR ...
Page 390: ...376 CHAPTER 22 I2C ...
Page 395: ...381 CHAPTER 22 I2C ...
Page 399: ...385 CHAPTER 22 I2C ...
Page 430: ...416 CHAPTER 23 10 BIT A D CONVERTER ...
Page 476: ...462 CHAPTER 24 LCD CONTROLLER ...
Page 482: ...468 CHAPTER 25 LOW VOLTAGE DETECTION RESET CIRCUIT ...
Page 494: ...480 CHAPTER 26 CLOCK SUPERVISOR ...
Page 507: ...493 CHAPTER 27 REAL TIME CLOCK ...
Page 523: ...509 CHAPTER 27 REAL TIME CLOCK ...
Page 532: ...518 CHAPTER 27 REAL TIME CLOCK ...
Page 536: ...522 CHAPTER 28 256 KBIT FLASH MEMORY ...
Page 554: ...540 CHAPTER 28 256 KBIT FLASH MEMORY ...
Page 564: ...550 CHAPTER 29 EXAMPLE OF SERIAL PROGRAMMING CONNECTION ...
Page 595: ...581 INDEX INDEX The index follows on the next page This is listed in alphabetic order ...
Page 596: ...582 INDEX Index ...
Page 597: ...583 INDEX ...
Page 600: ...586 Pin Function Index ...
Page 602: ......