4507_M Datasheet, PDF (135/216 Pages) Renesas Technology Corp – 4-BIT CISC SINGLE-CHIP MICROCOMPUTER 4500 SERIES

4507 Group
APPLICATION
2.2 Interrupts
➀ Disable Interrupts
Timer 2 interrupt is temporarily disabled.
Interrupt enable flag INTE “0”
b3
b0
Interrupt control register V1 0 ✕ ✕ ✕
All interrupts disabled (DI instruction)
Timer 2 interrupt occurrence disabled
(TV1A instruction)
➁ Stop Timer 2 Operation
Timer 2 and prescaler are temporarily stopped.
Dividing ratio of prescaler is selected.b3
b0
Timer control register W1 0 1 ✕ ✕
b3
b0
Timer control register W2 0 ✕ 0 1
Prescaler stop (TW1A instruction)
Prescaler divided by 16 selected for count source
Timer 2 stop (TW2A instruction)
Prescaler output selected for count source
➂ Set Timer Value
Timer 2 count time is set. (The formula is shown ❈A below.)
Timer 2 reload register R2 “5216” Timer count value 82 set (T2AB instruction)
➃ Clear Interrupt Request
Timer 2 interrupt activated condition is cleared.
Timer 2 interrupt request flag T2F _{“0”}
Timer 2 interrupt activated condition cleared
(SNZT2 instruction)
Note when the interrupt request is cleared
When ➃ is executed, considering the skip of the next instruction according to the
interrupt request flag T2F, insert the NOP instruction after the SNZT2 instruction.
➄ Start Timer 2 Operation
Timer 2 and prescaler temporarily stopped are restarted.
b3
b0
Timer control register W2 1 ✕ 0 1 Timer 2 operation start (TW2A instruction)
b3
b0
Timer control register W1 1 1 ✕ ✕ Prescaler operation start (TW1A instruction)
➅ Enable Interrupts
The timer 2 interrupt which is temporarily disabled is enabled.
b3
b0
Interrupt control register V1 1 ✕ ✕ ✕
Timer 2 interrupt occurrence enabled
(TV1A instruction)
Interrupt enable flag INTE “1”
All interrupts enabled (EI instruction)
Constant period interrupt execution start
❈A The prescaler dividing ratio and timer 2 count source to make the interrupt occur
every about 1 ms is set as follows.
–1
1 ms ≅ (4.0 MHz) ✕ 3
✕ 16 ✕ (82+1)
System clock Instruction Prescaler Timer 2
clock
dividing count
ratio
value
“✕”: it can be “0” or “1.”
Fig. 2.2.4 Timer 2 constant period interrupt setting example
Rev.2.01 Feb 04, 2005
REJ09B0195-0201
2-20