4513_03 Datasheet, PDF (126/210 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
2.2 Interrupts
ΠDisable Interrupts
Timer 3 interrupt is temporarily disabled.
Interrupt enable flag INTE “0”
All interrupts disabled (DI instruction)
Interrupt control register V2
b3
b0
!!! 0
Timer 3 interrupt occurrence disabled
(TV2A instruction)
 Stop Timer 3 Operation
Timer 3 and prescaler are temporarily stopped.
Dividing ratio of prescaler is selected.
Timer control register W1
b3
0
1
b0
!!
Prescaler stop (TW1A instruction)
Prescaler divided by 16 selected
Timer control register W3
b3
0!
0
b0
1
Timer 3 stop (TW3A instruction)
Prescaler selected for count source
Ž Set Timer Value
Timer 3 count time is set. (The formula is shown gA below.)
Timer 3 reload register R3 “5216” Timer count value 82 set (T3AB instruction)
 Clear Interrupt Request
Timer 3 interrupt activated condition is cleared.
Timer 3 interrupt request flag T3F “0”
g0 h
Timer 3 interrupt activated condition cleared
(SNZT3 instruction)
Note when the interrupt request is cleared
When  is executed, considering the skip of the next instruction according to the
interrupt request flag T3F, insert the NOP instruction after the SNZT3 instruction.
 Start Timer 3 Operation
Timer 3 and prescaler temporarily stopped are restarted.
b3
b0
Timer control register W3 1 ! 0 1 Timer 3 operation start (TW3A instruction)
b3
b0
Timer control register W1 1 1 ! ! Prescaler operation start (TW1A instruction)
‘ Enable Interrupts
The timer 3 interrupt which is temporarily disabled is enabled.
Interrupt control register V2
b3
b0
! !! 1
Timer 3 interrupt occurrence enabled
(TV2A instruction)
Interrupt enable flag INTE “1”
All interrupts enabled (EI instruction)
Constant period interrupt execution start
gA The prescaler dividing ratio and time 3 count value to make the interrupt occur every 1 ms are set as follows.
1 ms ≅ (4.0 MHz)^–1! 3
! 16 ! (82+1)
System clock Instruction Prescaler Timer 3
clock
dividing count
ratio
value
“!”: it can be “0” or “1.”
Fig. 2.2.7 Timer 3 constant period interrupt setting example
4513/4514 Group User’s Manual
2-23