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S1C88650 TECHNICAL MANUAL EPSON 127
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Interrupt and Standby Status)
5.14 Interrupt and Standby Status
■ Types of interrupts
4 systems and 31 types of interrupts have been
provided for the S1C88650.
External interrupt
•K00–K07 input interrupt (8 types)
Internal interrupt
•Clock timer interrupt (4 types)
•Programmable timer interrupt (16 types)
•Serial interface interrupt (3 types)
An interrupt factor flag that indicates the genera-
tion of an interrupt factor and an interrupt enable
register that sets enable/disable for interrupt
requests have been provided for each interrupt
and interrupt generation can be optionally set for
each factor.
In addition, an interrupt priority register has been
provided for each system of interrupts and the
priority of interrupt processing can be set to 3
levels in each system.
Figure 5.14.1 shows the configuration of the
interrupt circuit.
Refer to the explanations of the respective periph-
eral circuits for details on each interrupt.
■ HALT status
By executing the program's HALT instruction, the
S1C88650 enters the HALT status.
Since CPU operation stops in the HALT status,
power consumption can be reduced with only
peripheral circuit operation.
Cancellation of the HALT status is done by initial
reset or an optional interrupt request, and the CPU
restarts program execution from an exception
processing routine.
See the "S1C88 Core CPU Manual" for the HALT
status and reactivation sequence.
■ SLEEP status
By executing the program's SLP instruction, the
S1C88650 enters the SLEEP status.
Since the operation of the CPU and peripheral
circuits stop completely in the SLEEP status, power
consumption can be reduced even more than in the
HALT status.
Cancellation of the SLEEP status is done by initial
reset or an input interrupt from the input port. The
CPU reactivates after waiting 128/f
OSC1 or 512/
fOSC3 seconds of oscillation stabilization time (the
oscillation stabilization time varies depending on
the operating clock being used when the SLP
instruction is executed). At this time, the CPU
restarts program execution from an exception
processing routine (input interrupt routine).
Note: The oscillation becomes unstable for a while
after SLEEP status is cancelled, the wait
time for restarting the CPU may be longer
than 128/f
OSC1
or 512/f
OSC3
seconds.
5.14.1 Interrupt generation conditions
The interrupt factor flags that indicate the genera-
tion of their respective interrupt factors are pro-
vided for the previously indicated 4 systems and 31
types of interrupts and they will be set to "1" by the
generation of a factor.
In addition, interrupt enable registers with a 1 to 1
correspondence to each of the interrupt factor flags
are provided. An interrupt is enabled when "1" is
written and interrupt is disabled when "0" is
written.
The CPU manages the enable/disable of interrupt
requests at the interrupt priority level. An interrupt
priority register that sets the priority level is
provided for each of the interrupts of the 4 systems
and the CPU accepts only interrupts above the level
that has been indicated with the interrupt flags (I0
and I1).
Consequently, the following three conditions are
necessary for the CPU to accept the interrupt.
(1) The interrupt factor flag has been set to "1" by
generation of an interrupt factor.
(2) The interrupt enable register corresponding to
the above has been set to "1".
(3) The interrupt priority register corresponding to
the above has been set to a priority level higher
than the interrupt flag (I0 and I1) setting.
The CPU initially samples the interrupt for the first
op-code fetch cycle of each instruction. Thereupon,
the CPU shifts to the exception processing when the
above mentioned conditions have been established.
See the "S1C88 Core CPU Manual" for the exception
processing sequence.