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Internal
address bus
Internal
write signal
CMIEA
CMFA
CMIA
interrupt signal
Figure 5-8 Contention between Interrupt Generation and Disabling
The above contention will not occur if an enable bit or interrupt source flag is cleared to 0 while
the interrupt is masked.
5.5.2
Instructions that Disable Interrupts
Instructions that disable interrupts are LDC, ANDC, ORC, and XORC. After any of these
instructions is executed, all interrupts including NMI are disabled and the next instruction is
always executed. When the I bit is set by one of these instructions, the new value becomes valid
two states after execution of the instruction ends.
5.5.3
Times when Interrupts are Disabled
There are times when interrupt acceptance is disabled by the interrupt controller.
The interrupt controller disables interrupt acceptance for a 3-state period after the CPU has
updated the mask level with an LDC, ANDC, ORC, or XORC instruction.
TCR write cycle by CPU
TCR address
CMIA exception handling
115
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