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CHAPTER 6 INTERRUPTS
MB90560 series
6.4
Hardware Interrupts
The hardware interrupt function temporarily interrupts the program being executed by
the CPU and transfers control to a user-defined interrupt processing program in
response to an interrupt signal from a peripheral function.
The extended intelligent I/O service (EI
2
OS) and external interrupts are executed as a
type of hardware interrupt.
I
Hardware interrupts
G
Hardware interrupt function
The hardware interrupt function compares the interrupt level of the interrupt request signal output
by a peripheral function with the interrupt level mask register (ILM) in the CPU processor status
(PS). The function then references the contents of the I flag in the processor status (PS) through
the hardware and decides if the interrupt can be accepted.
When the hardware interrupt is accepted, the CPU internal registers are automatically saved on
the system stack. The currently requested interrupt level is stored in the interrupt level mask
register (ILM), and the function branches to the corresponding interrupt vector.
G
Multiple interrupts
Multiple hardware interrupts can be activated.
G
Extended intelligent I/O service (EI
2
OS)
EI
2
OS is an automatic transfer function between memory and I/O. When the specified transfer
count has been completed, a hardware interrupt is activated. Multiple EI
2
OS activation is not
possible to occur. During EI
2
OS processing, all other interrupt requests and EI
2
OS requests are
held.
G
External interrupt
An external interrupt (including wake-up interrupts) is accepted from a peripheral function
(interrupt request detection circuit) as a hardware interrupt.
G
Interrupt vector
Interrupt vector tables referenced during interrupt processing are allocated to memory at
“FFFC00
H
“ to “FFFFFF
H
”. These tables are shared by software interrupts.
See Section 6.2, "Interrupt causes and Interrupt Vectors," for more information about the
allocation of interrupt numbers and interrupt vectors.