Renesas 4514 - Manual (Page 139)

APPLICATION
2.3 Timers
2-36 4513/4514 Group User’s Manual
Fig. 2.3.7 Timer start by external input setting example (1)
0
b3 b0
➀ 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)
INT0 interrupt occurrence disabled 0
b3 b0
0 0
➁ 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 4 selected
0
➂ Set Timer Value
Timer 1 count time is set.
Timer 1 reload register R1 “52 16 ” Timer count value 82 set (T1AB instruction)
b3 b0
1
➃ Set Port
P3 0 /INT0 pin is set to INT0 input.
Port P3 0 output latch ✕ ✕ ✕ INT0 input set (OP3A instruction)
b3 b0
1
➄ Set Valid Waveform
Valid waveform of INT0 pin is selected. Timer 1 control is enabled.
Interrupt control register I1 ✕ Rising edge detected (TI1A instruction) 1 0
g0 h
➅ Clear Interrupt Request
Timer 1 interrupt activated condition is cleared.
INT0 interrupt activated condition is cleared.
Timer 1 interrupt request flag T1F
INT0 interrupt request flag EXF0
“0”
Timer 1 interrupt activated condition cleared
(SNZT1 instruction)
INT0 interrupt activated condition cleared
(SNZ0 instruction)
“0”
Note when the interrupt request is cleared
When ➅ is executed, considering the skip of the next instruction according to the
interrupt request flags T1F and EXF0, insert the NOP instruction after the SNZT1
and SNZ0 instructions.
b3 b0
1
➆ 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)
✕ ✕ ✕
Timer start by external input
“ ✕ ”: it can be “0” or “1.”