s-35392a Seiko Instruments Inc., s-35392a Datasheet - Page 28

• Manufacturer Part Number: s-35392a
• Description: 2-wire Real-time Clock
• Manufacturer: Seiko Instruments Inc.

28
2-WIRE REAL-TIME CLOCK
S-35392A
Serial Interface
The S-35392A receives various commands via I
follows.
1. Start condition
2. Stop condition
3. Data transfer and acknowledgment signal
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-35392A 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 29, in case that the S-35392A 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-35392A sends an acknowledgment signal back, and set the SDA line to
“L” at the 9-bit clock pulse. The S-35392A does not output an acknowledgment signal is that the access is not being
done regularly.
(Output from
master device)
S-35392A)
(Input from
S-35392A)
(Output from
SDA
SCL
SDA
SCL
SDA
Start condition
Start condition
t
SU.STA
Figure 29 Output Timing of Acknowledgment Signal
t
SU.DAT
HD.STA
t
SU.DAT
and t
Figure 28 Start/Stop Conditions
1
HD. DAT
Seiko Instruments Inc.
2
t
C-bus serial interface to Read/Write data. Regarding transmission is as
High-Z
HD.DAT
when changing the SDA line. If the SDA line changes while the SCL line
8
Stop condition
t
SU.STO
t
PD
Output acknowledgment
SDA is released
High-Z
(“L” active)
9
Rev.1.3
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