Renesas 4514 - Manual (Page 40)

4513/4514 Group User’s Manual
HARDWARE
1-27
FUNCTION BLOCK OPERATIONS
(1) External 0 interrupt request flag (EXF0)
External 0 interrupt request flag (EXF0) is set to “1” when a valid
waveform is input to P3 0 /INT0 pin.
The valid waveforms causing the interrupt must be retained at their
level for 4 clock cycles or more of the system clock (Refer to Figure
16).
The state of EXF0 flag can be examined with the skip instruction
(SNZ0). Use the interrupt control register V1 to select the interrupt
or the skip instruction. The EXF0 flag is cleared to “0” when an in-
terrupt occurs or when the next instruction is skipped with the skip
instruction.
The P3 0 /INT0 pin need not be selected the external interrupt input
INT0 function or the normal I/O port P3 0 function. However, the
EXF0 flag is set to “1” when a valid waveform is input even if it is
used as an I/O port P3 0 .
• External 0 interrupt activated condition
External 0 interrupt activated condition is satisfied when a valid
waveform is input to P3 0 /INT0 pin.
The valid waveform can be selected from rising waveform, falling
waveform or both rising and falling waveforms. An example of
how to use the external 0 interrupt is as follows.
➀ Select the valid waveform with the bits 1 and 2 of register I1.
➁ Clear the EXF0 flag to “0” with the SNZ0 instruction.
➂ Set the NOP instruction for the case when a skip is performed
with the SNZ0 instruction.
➃ Set both the external 0 interrupt enable bit (V1 0 ) and the INTE
flag to “1.”
The external 0 interrupt is now enabled. Now when a valid wave-
form is input to the P3 0 /INT0 pin, the EXF0 flag is set to “1” and the
external 0 interrupt occurs.
(2) External 1 interrupt request flag (EXF1)
External 1 interrupt request flag (EXF1) is set to “1” when a valid
waveform is input to P3 1 /INT1 pin.
The valid waveforms causing the interrupt must be retained at their
level for 4 clock cycles or more of the system clock (Refer to Figure
16).
The state of EXF1 flag can be examined with the skip instruction
(SNZ1). Use the interrupt control register V1 to select the interrupt
or the skip instruction. The EXF1 flag is cleared to “0” when an in-
terrupt occurs or when the next instruction is skipped with the skip
instruction.
The P3 1 /INT1 pin need not be selected the external interrupt input
INT1 function or the normal I/O port P3 1 function. However, the
EXF1 flag is set to “1” when a valid waveform is input even if it is
used as an I/O port P3 1 .
• External 1 interrupt activated condition
External 1 interrupt activated condition is satisfied when a valid
waveform is input to P3 1 /INT1 pin.
The valid waveform can be selected from rising waveform, falling
waveform or both rising and falling waveforms. An example of
how to use the external 1 interrupt is as follows.
➀ Select the valid waveform with the bits 1 and 2 of register I2.
➁ Clear the EXF1 flag to “0” with the SNZ1 instruction.
➂ Set the NOP instruction for the case when a skip is performed
with the SNZ1 instruction.
➃ Set both the external 1 interrupt enable bit (V1 1 ) and the INTE
flag to “1.”
The external 1 interrupt is now enabled. Now when a valid wave-
form is input to the P3 1 /INT1 pin, the EXF1 flag is set to “1” and the
external 1 interrupt occurs.