I-70
EPSON
S1C6S3N2 TECHNICAL HARDWARE
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Stopwatch Counter)
Data (BCD) of the 1/100 sec column of the stopwatch coun-
ter can be read out. These four bits are read-only, and
cannot be used for writing operations.
At initial reset, the counter data is set to "0H".
Data (BCD) of the 1/10 sec column of the stopwatch counter
can be read out. These four bits are read-only, and cannot
be used for writing operations.
At initial reset, the counter data is set to "0H".
These registers are used to select whether to mask the
stopwatch counter interrupt.
When "1" is written :
Enabled
When "0" is written :
Masked
Read-out :
Valid
The interrupt mask registers (EISWIT0, EISWIT1) are used
to separately select whether to mask the 10 Hz and 1 Hz
interrupts.
At initial reset, these registers are both set to "0".
These flags indicate the status of the stopwatch counter
interrupt.
When "1" is read out : Interrupt has occurred
When "0" is read out : Interrupt has not occurred
Writing :
Invalid
The interrupt factor flags (SWIT0, SWIT1) correspond to the 10
Hz and 1 Hz interrupts respectively. With these flags, the
software can judge whether a stopwatch counter interrupt has
occurred. However, regardless of the interrupt mask register
setting, these flags are set to "1" by the counter overflow.
These flags are reset when read out by the software.
Reading of interrupt factor flags is available at EI, but be
careful in the following cases.
If the interrupt mask register value corresponding to the
interrupt factor flags to be read is set to "1", an interrupt
request will be generated by the interrupt factor flags set
timing, or an interrupt request will not be generated.
Be very careful when interrupt factor flags are in the same
address.
At initial reset, these flags are set to "0".
SWL0–SWL3:
Stopwatch counter
1/100 sec (071H)
SWH0–SWH3:
Stopwatch counter
1/10 sec (072H)
EISWIT0, EISWIT1:
Interrupt mask register
(076H·D0 and D1)
SWIT0, SWIT1:
Interrupt factor flag
(07AH·D0 and D1)
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