S-35390A Datasheet, PDF (29/54 Pages) Seiko Instruments Inc – 2-WIRE REAL-TIME CLOCK

Rev.2.4_00
2-WIRE REAL-TIME CLOCK
S-35390A
„ Serial Interface
The S-35390A 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-35390A gets standby.
t_SU.STA t_HD.STA
t_SU.STO
SCL
SDA
Start condition
Figure 32 Start/Stop Conditions
Stop condition
3. Data transfer 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 t_SU.DAT and t_{HD. 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 33, in case that the S-35390A is the device working for
receiving data and the master device is the one working for sending data; when the 8th clock pulse falls, the master
device releases the SDA line. After that, the S-35390A sends an acknowledgment signal back, and set the SDA line to
“L” at the 9th clock pulse. The S-35390A does not output an acknowledgment signal is that the access is not being done
regularly.
SCL
(Input from
S-35390A)
SDA
(Output from
master device)
SDA
(Input from
S-35390A)
1
8
9
t_SU.DAT
t_HD.DAT
SDA is released
High-Z
Output acknowledgment
(“L” active)
Start condition
High-Z
t_PD
Figure 33 Output Timing of Acknowledgment Signal
Seiko Instruments Inc.
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