RL78/F13, F14 CHAPTER 21 INTERRUPT FUNCTIONS
R01UH0368EJ0210 Rev.2.10 1508
Dec 10, 2015
21.4.2 Software interrupt request acknowledgment
A software interrupt request is acknowledged by BRK instruction execution. Software interrupts cannot be disabled.
If a software interrupt request is acknowledged, the contents are saved into the stacks in the order of the program status
word (PSW), then program counter (PC), the IE flag is reset (0), and the contents of the vector table (0007EH, 0007FH) are
loaded into the PC and branched.
Restoring from a software interrupt is possible by using the RETB instruction.
Caution Can not use the RETI instruction for restoring from the software interrupt.
21.4.3 Multiple interrupt servicing
Multiple interrupt servicing occurs when another interrupt request is acknowledged during execution of an interrupt.
Multiple interrupt servicing does not occur unless the interrupt request acknowledgment enabled state is selected (IE =
1). When an interrupt request is acknowledged, interrupt request acknowledgment becomes disabled (IE = 0). Therefore,
to enable multiple interrupt servicing, it is necessary to set (1) the IE flag with the EI instruction during interrupt servicing to
enable interrupt acknowledgment.
Moreover, even if interrupts are enabled, multiple interrupt servicing may not be enabled, this being subject to interrupt
priority control. Two types of priority control are available: default priority control and programmable priority control.
Programmable priority control is used for multiple interrupt servicing.
In the interrupt enabled state, if an interrupt request with a priority higher than that of the interrupt currently being serviced
is generated, it is acknowledged for multiple interrupt servicing. If an interrupt with a priority equal to or lower than that of
the interrupt currently being serviced is generated during interrupt servicing, it is not acknowledged for multiple interrupt
servicing. However, when setting the IE flag to 1 during the interruption at level 0, other level 0 interruptions can be allowed.
Interrupt requests that are not enabled because interrupts are in the interrupt disabled state or because they have a lower
priority are held pending. When servicing of the current interrupt ends, the pending interrupt request is acknowledged
following execution of at least one main processing instruction execution.
Table 21-5 shows relationship between interrupt requests enabled for multiple interrupt servicing and Figure 21-14 shows
multiple interrupt servicing examples.
To Next Page
Loading...
Need help?
General
