215
CHAPTER 14 WATCH COUNTER
14.5
Explanation of Watch Counter Operations and Setup
Procedure Example
The watch counter counts down for the number of times specified in the count value by
RCTR5 to RCTR0 bits, using the count clock selected by CS1 and CS0 bits, when the
ISEL bit is set to "1". Once the counter underflows, WCFLG bit of the WCSR register is
set to "1", generating an interrupt.
■
Setup Procedure of Watch Counter
The setup procedure of the watch counter is described below.
(1) Select the count clock (CS1 and CS0 bits) and set the counter reload value (RCTR5 to RCTR0 bits).
(2) Set the ISEL bit of the WCSR register to "1" to start a down count and enable interrupts. Also disable
interrupts of the watch prescaler.
The watch counter performs counting by using a divided clock (asynchronous) from the watch
prescaler. An error of up to one count clock may occur at the beginning of a count cycle, depending on
the timing for setting the ISEL bit to "1".
(3) When the counter underflows, the WCFLG bit of the WCSR register is set to "1", generating an
interrupt.
(4) Write "0" to the WCFLG bit to clear it.
(5) If RCTR5 to RCTR0 bits are modified during counting, the reload value will be updated during a
reload after the counter is set to "1".
(6) When writing "0" to the ISEL bit, the counter becomes "0" and stops operation.
Figure 14.5-1 Descriptive Diagram of Watch Counter Operation
RCTR5 to 0
WCFLG
ISEL
7
9
CS1,0
"1,1"
(1)
(2)
(3)
(4)
(6)
CTR5 to 0
7
0
6
5
4
3
2 1
9 8
7
6
5 4
0
(5)
Count clock
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: ......