HD6432646 Hitachi, HD6432646 Datasheet - Page 157

• Manufacturer Part Number: HD6432646
• Description: (HD64F264x Series) 16-Bit Microcomputer
• Manufacturer: Hitachi

Table 5-10 Number of States in Interrupt Handling Routine Execution Statuses
Symbol
Instruction fetch
Branch address read
Stack manipulation
Legend
m: Number of wait states in an external device access.
5.5
5.5.1
When an interrupt enable bit is cleared to 0 to disable interrupts, the disabling becomes effective
after execution of the instruction.
In other words, when an interrupt enable bit is cleared to 0 by an instruction such as BCLR or
MOV, if an interrupt is generated during execution of the instruction, the interrupt concerned will
still be enabled on completion of the instruction, and so interrupt exception handling for that
interrupt will be executed on completion of the instruction. However, if there is an interrupt
request of higher priority than that interrupt, interrupt exception handling will be executed for the
higher-priority interrupt, and the lower-priority interrupt will be ignored.
The same also applies when an interrupt source flag is cleared to 0.
Figure 5-8 shows an example in which the TCIEV bit in the TPU’s TIER0 register is cleared to 0.
Usage Notes
Contention between Interrupt Generation and Disabling
S
S
S
I
J
K
Internal
Memory
1
8 Bit Bus
2-State
Access
4
Object of Access
3-State
Access
6+2m
External Device
16 Bit Bus
2-State
Access
2
3-State
Access
3+m
123