|
4501_M Datasheet, PDF (135/212 Pages) Renesas Technology Corp – 4-BIT CISC SINGLE-CHIP MICROCOMPUTER 4500 SERIES | |||
|
◁ |
4501 Group
APPLICATION
2.2 Interrupts
â Disable Interrupts
Timer 1 interrupt is temporarily disabled.
Interrupt enable flag INTE â0â
All interrupts disabled (DI instruction)
b3
b0 Timer 1 interrupt occurrence disabled
Interrupt control register V1 â 0 â â (TV1A instruction)
â Stop Timer Operation
Timer 1 and prescaler are temporarily stopped.
Dividing ratio of prescaler is selected.
b3
b0 Timer 1 stop (TW1A instruction)
Timer control register W1 0 1 0 0 Prescaler stop
Prescaler divided by 16 selected
â Set Timer Value
Timer 1 count time is set. (The formula is shown âA below.)
Timer 1 reload register R1 â5216â Timer count value 82 set (T1AB instruction)
â Clear Interrupt Request
Timer 1 interrupt activated condition is cleared.
Timer 1 interrupt request flag T1F â0â
Timer 1 interrupt activated condition cleared
(SNZT1 instruction)
Note when the interrupt request is cleared
When â is executed, considering the skip of the next instruction according to the
interrupt request flag T1F, insert the NOP instruction after the SNZT1 instruction.
â Start Timer Operation
Timer 1 and prescaler temporarily stopped are restarted.
b3
b0
Timer control register W1 1 1 1 0 Timer 1 operation start (TW1A instruction)
Prescaler operation start
â
Enable Interrupts
The Timer 1 interrupt which is temporarily disabled is enabled.
Interrupt control register V1
b3
b0
â1ââ
Timer 1 interrupt occurrence enabled
(TV1A instruction)
Interrupt enable flag INTE â1â
All interrupts enabled (EI instruction)
Constant period interrupt execution start
âA The prescaler dividing ratio and timer 1 count value to make the interrupt occur every 1 ms are set as follows.
1 ms â
(4.0 MHz)â1â 3
â 16 â (82+1)
System clock Instruction Prescaler Timer 1
clock
dividing count
ratio
value
âââ: it can be â0â or â1.â
Fig. 2.2.3 Timer 1 constant period interrupt setting example
Rev.2.01 Feb 07, 2005
REJ09B0192-0201
2-18
|
▷ |