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S-35399A02 Datasheet, PDF (35/55 Pages) Seiko Instruments Inc – 2-WIRE REAL-TIME CLOCK
Rev.1.0_00
2-WIRE REAL-TIME CLOCK
S-35399A02
„ Serial Interface
The S-35399A02 receives various commands via I2C-bus serial interface to Read/Write data. Regarding transmission is as
follows.
1. Start condition
A start condition is when the SDA line changes “H” to “L” when the SCL line is in “H”, so that the access starts.
2. Stop condition
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-35399A02 gets standby.
tSU.STA tHD.STA
tSU.STO
SCL
SDA
Start condition
Figure 40 Start/Stop Conditions
Stop condition
3. Data transmission and acknowledgment signal
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 tSU.DAT and tHD. DAT when changing the SDA line. If the SDA line changes while the SCL line
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 41, in case that the S-35399A02 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-35399A02 sends an acknowledgment signal back, and set the SDA line
to “L” at the 9-bit clock pulse. The S-35399A02 does not output an acknowledgment signal is that the access is not
being done regularly.
SCL
(Input from
S-35399A02)
SDA
(Output from
master device)
SDA
(Output from
S-35399A02)
1
8
9
tSU.DAT
tHD.DAT
SDA is released
High-Z
Output acknowledgment
(“L” active)
Start condition
High-Z
tPD
Figure 41 Output Timing of Acknowledgment Signal
Seiko Instruments Inc.
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