s-35399a03 Seiko Instruments Inc., s-35399a03 Datasheet - Page 32

• Manufacturer Part Number: s-35399a03
• Description: 2-wire Real-time Clock
• Manufacturer: Seiko Instruments Inc.

32
2-WIRE REAL-TIME CLOCK
S-35399A03
Serial Interface
The S-35399A03 receives various commands via I
follows.
1. Start condition
2. Stop condition
3. Data transmission and acknowledgment signal
SDA
SCL
A start condition is when the SDA line changes “H” to “L” when the SCL line is in “H”, so that the access starts.
A stop condition is when the SDA line changes “L” to “H” when the SCL line is in “H”, and the access stops, so that the
S-35399A03 gets standby.
Data transmission is performed for every 1-byte, after detecting a start condition. Transmit data while the SCL line is in
“L”, and be careful of spec of t
is in “H”, the data will be recognized as start/stop condition in spite of data transmission. Note that by this case, the
access will be interrupted.
During data transmission, every moment receiving 1-byte data, the devices which work for receiving data send an
acknowledgment signal back. For example, as seen in Figure 34 , in case that the S-35399A03 is the device working for
receiving data and the master device is the one working for sending data; when the 8-bit clock pulse falls, the master
device releases the SDA line. After that, the S-35399A03 sends an acknowledgment signal back, and set the SDA line
to “L” at the 9-bit clock pulse. The S-35399A03 does not output an acknowledgment signal is that the access is not
being done regularly.
S-35399A03)
S-35399A03)
master device)
(Output from
(Output from
(Input from
SDA
SCL
SDA
t
SU.STA
Start condition
Start condition
t
HD.STA
Figure 34 Output Timing of Acknowledgment Signal
SU.DAT
t
SU.DAT
and t
Figure 33 Start/Stop Conditions
HD. DAT
1
Seiko Instruments Inc.
2
t
when changing the SDA line. If the SDA line changes while the SCL line
HD.DAT
C-bus serial interface to Read/Write data. Regarding transmission is as
High-Z
8
t
PD
t
SU.STO
Output acknowledgment
Stop condition
SDA is released
High-Z
(“L” active)
9
Rev.1.0
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