Renesas 4513 Network Card User Manual


 
APPLICATION
2.3 Timers
2-32
4513/4514 Group User’s Manual
Fig. 2.3.3 Constant period measurement setting example
g0 h
0
b3 b0
Disable Interrupts
Timer 1 interrupt is temporarily disabled.
Interrupt enable flag INTE
Interrupt control register V1
“0”
✕✕
All interrupts disabled (DI instruction)
Timer 1 interrupt occurrence disabled
(TV1A instruction)
b3 b0
01
Stop Timer Operation
Timer 1 and prescaler are temporarily stopped.
Dividing ratio of prescaler is selected.
Timer control register W1
Timer 1 stop (TW1A instruction)
Prescaler stop
Prescaler divided by 16 selected
0
Set Timer Value
Timer 1 count time is set. (The formula is shown A below.)
Timer 1 reload register R1
“F9
16
Timer count value 249 set (T1AB instruction)
Clear Interrupt Request
Timer 1 interrupt activated condition is cleared.
Timer 1 interrupt request flag T1F
“0”
Timer 1 interrupt activated condition cleared
(SNZT1 instruction)
Note when the interrupt request is cleared
When is executed, considering the skip of the next instruction according to the
interrupt request flag T1F, insert the NOP instruction after the SNZT1 instruction.
Start Timer 1 Operation
Timer 1 and prescaler temporarily stopped are restarted.
Timer 1 operation start (TW1A instruction)
Prescaler operation start
b3 b0
11
Timer control register W1
1
b3 b0
1
Enable Interrupts
The timer 1 interrupt which is temporarily disabled is enabled.
Interrupt control register V1
Interrupt enable flag INTE
“1”
Timer 1 interrupt occurrence enabled
(TV1A instruction)
All interrupts enabled (EI instruction)
✕✕
Constant period interrupt execution start
A The prescaler dividing ratio and timer 1 count value to make the interrupt occur
every 4 ms are set as follows.
4 ms (4.0 MHz) 3 16 (249+1)
–1
System clock Instruction
clock
Prescaler
dividing
ratio
Timer 1
count
value
”: it can be “0” or “1.”