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4.9.4 I/O memory of stopwatch timer
Table 4.9.4.1 shows the I/O addresses and the control bits for the stopwatch timer.
Register
Address
D3
D2
0
0
SWRST SWRUN
FF7CH
R
SWD3
SWD2
SWD1
FF7DH
R
SWD7
SWD6
SWD5
FF7EH
R
0
0
EISW1 EISW10
FFE7H
R
0
0
FFF7H
R
*1 Initial value at initial reset
*2 Not set in the circuit
*3 Constantly "0" when being read
SWD0–SWD7: Stopwatch timer data (FF7DH, FF7EH)
The 1/100 sec and the 1/10 sec data (BCD) can be read from SWD0–SWD3 and SWD4–SWD7, respec-
tively. These eight bits are read only, and writing operations are invalid.
At initial reset, the timer data is initialized to "00H".
SWRST: Stopwatch timer reset (FF7CH•D1)
When "1" is written: Stopwatch timer reset
When "0" is written: No operation
Reading: Always "0"
The stopwatch timer is reset by writing "1" to SWRST. All timer data is set to "0". When the stopwatch
timer is reset in the RUN status, operation restarts immediately. Also, in the STOP status the reset data is
maintained. No operation results when "0" is written to SWRST.
This bit is write-only, and so is always "0" at reading.
SWRUN: Stopwatch timer RUN/STOP control register (FF7CH•D0)
Controls RUN/STOP of the stopwatch timer.
When "1" is written: RUN
When "0" is written: STOP
Reading: Valid
The stopwatch timer enters the RUN status when "1" is written to the SWRUN register, and the STOP
status when "0" is written.
In the STOP status, the timer data is maintained until the next RUN status or the timer is reset. Also,
when the STOP status changes to the RUN status, the data that is maintained can be used for resuming
the count.
S1C63454 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Stopwatch Timer)
Table 4.9.4.1 Control bits of stopwatch timer
∗1
D1
D0
Name Init
∗3
∗2
0
–
∗3
∗2
0
–
∗3
SWRST
Reset
W
R/W
SWRUN
0
SWD3
0
SWD0
SWD2
0
SWD1
0
SWD0
0
SWD7
0
SWD4
SWD6
0
SWD5
0
SWD4
0
∗3
∗2
0
–
∗3
∗2
0
–
EISW1
0
R/W
EISW10
0
∗3
∗2
0
–
ISW1
ISW10
∗3
∗2
0
–
ISW1
0
R/W
ISW10
0
1
0
Unused
Unused
Reset
Invalid
Stopwatch timer reset (writing)
Run
Stop
Stopwatch timer Run/Stop
Stopwatch timer data
BCD (1/100 sec)
Stopwatch timer data
BCD (1/10 sec)
Unused
Unused
Enable
Mask
Interrupt mask register (Stopwatch timer 1 Hz)
Enable
Mask
Interrupt mask register (Stopwatch timer 10 Hz)
(R)
(R)
Unused
Yes
No
Unused
(W)
(W)
Interrupt factor flag (Stopwatch timer 1 Hz)
Reset
Invalid
Interrupt factor flag (Stopwatch timer 10 Hz)
EPSON
Comment
57
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