HD6432621 Hitachi, HD6432621 Datasheet - Page 155

• Manufacturer Part Number: HD6432621
• Description: (HD64F262x Series) 16-Bit Microcomputer
• Manufacturer: Hitachi

5.4.2
Enabling and disabling of IRQ interrupts and on-chip supporting module interrupts can be set by
means of the I bit in the CPU’s CCR. Interrupts are enabled when the I bit is cleared to 0, and
disabled when set to 1.
Figure 5-5 shows a flowchart of the interrupt acceptance operation in this case.
[1] If an interrupt source occurs when the corresponding interrupt enable bit is set to 1, an interrupt
[2] The I bit is then referenced. If the I bit is cleared to 0, the interrupt request is accepted. If the I
[3] Interrupt requests are sent to the interrupt controller, the highest-ranked interrupt according to
[4] When an interrupt request is accepted, interrupt exception handling starts after execution of the
[5] The PC and CCR are saved to the stack area by interrupt exception handling. The PC saved on
[6] Next, the I bit in CCR is set to 1. This masks all interrupts except NMI.
[7] A vector address is generated for the accepted interrupt, and execution of the interrupt handling
request is sent to the interrupt controller.
bit is set to 1, only an NMI interrupt is accepted, and other interrupt requests are held pending.
the priority system is accepted, and other interrupt requests are held pending.
current instruction has been completed.
the stack shows the address of the first instruction to be executed after returning from the
interrupt handling routine.
routine starts at the address indicated by the contents of that vector address.
Interrupt Control Mode 0
111