I-92
EPSON
S1C6S3N2 TECHNICAL HARDWARE
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Interrupt and HALT)
PC
Value
Interrupt Request
PCS3
1
Stopwatch interrupt
Enabled
0
Masked
PCS2
1
Timer interrupt
Enabled
0
Masked
PCS1
1
Input (K00–K03) interrupt
Enabled
0
Masked
PCS0
1
Input (K10) interrupt or
Enabled
0
Masked
When an interrupt request is input to the CPU, the CPU
begins interrupt processing. After the program being exe-
cuted is terminated, the interrupt processing is executed in
the following order.
➀
The address data (value of program counter) of the pro-
gram to be executed next is saved in the stack area (RAM).
➁
The interrupt request causes the value of the interrupt
vector (page 1, 01H–0FH) to be set in the program counter.
➂
The program at the specified address is executed (execu-
tion of interrupt processing routine by software).
Table 4.13.3 shows the correspondence of interrupt re-
quests and interrupt vectors.
The processing in
➀
and
➁
above take 12 cycles of the CPU
system clock.
The four low-order bits of the program counter are indirectly
addressed through the interrupt request.
Interrupt vectors
Table 4.13.3
Interrupt request and
interrupt vectors
Note
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