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86 EPSON S1C6200/6200A CORE CPU MANUAL
APPENDIX A. S1C6200A (ADVANCED S1C6200) CORE CPU
<Reference 1> Writing on the interrupt mask register during EI
This section describes the operation for writing on the interrupt mask register during EI (enable interrupt
flag) in the regular 1-chip micro controller which uses S1C6200 Core CPU and in the regular 1-chip micro
controller which uses S1C6200A Core CPU. For information on accurate operation, see the respective
hardware manuals of the S1C62 Family.
Table A2.2.2 Writing on the interrupt mask register at EI
Writing on the interrupt mask register at EI
S1C6200
Not possible
S1C6200A
Possible
CPU Core
The operation during the instruction execution for writing "0" (i.e., to mask the interrupt factor) on the
interrupt mask register at EI is shown in Figure A2.2.2. At this point, the interrupt is masked 0.5 clock
before the start of the instruction execution through the 0.5 clock advance operation.
Moreover, during the instruction execution for writing "1" (i.e., to cancel the interrupt mask) on the mask
register at EI, it is the same as the ordinary interrupt timing as shown in Figure A2.2.2. In other words, if
the interrupt factor flag value is set to "1", the interrupt processing by hardware will start in the next
instruction execution cycle 0.5 clock before the completion of the instruction execution.
Fetch Execute Fetch Execute Fetch Execute Fetch
"0" is written to the interrupt mask register
Execute next instruction INT1(interrupt processing)
Clock
Status
Instruction
Corresponding
interrupt factor flag
Interrupt request
"1" is written to the interrupt mask register
Fig. A2.2.2 Writing on the interrupt mask register and interrupt request generation
<Reference 2> Reading the interrupt factor flag during EI
This section describes the operation for reading the interrupt factor flag during EI (enable interrupt flag) in
the regular 1-chip micro controller which uses S1C6200 Core CPU and in the regular 1-chip micro control-
ler which uses S1C6200A Core CPU. For information on accurate operation, see the respective hardware
manuals of the S1C62 Family.
Table A2.2.3 Reading the interrupt factor flag at EI
Reading the interrupt factor flag at EI
S1C6200
Not possible
S1C6200A
Possible
CPU Core
At EI, reading the interrupt factor flag is possible but caution must be observed in the following case: when
the value of the interrupt mask register corresponding to the interrupt factor flag which is to be read is set
to "1" (unmasked). In this case, interrupt request may be issued to the CPU due to the timing by which the
interrupt factor flag is set to "1", or the interrupt factor flag may be cleared by reading it and hence inter-
rupt request will not be issued.
Particularly when there are multiple interrupt factor flags in the same address, extra caution is required.