HD6433044 Hitachi Semiconductor, HD6433044 Datasheet - Page 123

• Manufacturer Part Number: HD6433044
• Description: (HD64 Series) Hitachi Single-Chip Microcomputer
• Manufacturer: Hitachi Semiconductor

2. IRQaF flag clear and IRQbF flag generation compete (IRQaF flag setting).
In all of the setting conditions 1 to 3 and occurrence conditions 1 and 2 are generated, IRQbF
clears in error during ISR write for occurrence condition 2 and interrupt processing is not carried
out. However, if IRQbF flag reaches 0 between occurrence conditions 1 and 2, IRQbF flag does
not clear in error.
In this situation, conduct one of the following countermeasures.
Countermeasure 1
When IRQaF flag clears, do not use the bit computation command, read the ISR in bytes. When
IRQaF only is 0 write all other bits as 1 in bytes.
For example, if a = 0
IRQaF
IRQbF
(The ISR read needed for IRQaF flag clear was at IRQbF = 0 but in the time taken for ISR
write, IRQbF = 1 was reached.)
MOV.B @ISR,R0L
MOV.B #HFE,R0L
Figure 5-9 IRQnF Flag When Interrupt Processing Is Not Conducted
Occurrence condition 1
Read
Read
1
1
Write
Write
0
1
Execution
IRQb
109
Occurrence condition 2
Clear in error
Read
Read
1
0
Write
Write
0
0