S-35390A Datasheet, PDF (35/54 Pages) Seiko Instruments Inc – 2-WIRE REAL-TIME CLOCK

Rev.2.4_00
2-WIRE REAL-TIME CLOCK
S-35390A
„ Reset After Communication Interruption
In case of communication interruption in the S-35390A, for example, during communication the power supply voltage drops
so that only the master device is reset; the S-35390A does not operate the next procedure because the internal circuit
keeps the state prior to interruption. The S-35390A does not have a reset pin so that users usually reset its internal circuit by
inputting a stop condition. However, if the SDA line is outputting “L” (during output of acknowledgment signal or Read), the
S-35390A does not accept a stop condition from the master device. In this case, users are necessary to finish
acknowledgment output or Read the SDA line. Figure 45 shows how to reset. First, input a start condition from the master
device (The S-35390A cannot detect a start condition because the SDA line in the S-35390A is outputting “L”). Next, input a
clock pulse equivalent to 7-byte data access (63-clock) from the SCL line. During this, release the SDA line for the master
device. By this procedure, SDA I/O before interruption is finished, so that the SDA line in the S-35390A is released. After
that, inputting a stop condition resets the internal circuit so that restore the regular communication. This reset procedure is
recommended to perform at initialization of the system after rising the master device’s power supply voltage.
Start
condition
Clocks equivalent to 7-byte data access
Stop
condition
SCL
1
2
8
9
62
63
SDA
(Output from
master device)
SDA
(Output from
“L”
S-35390A)
SDA
“L”
“L” or High-Z
“L” or High-Z
High-Z
Figure 45 How to Reset
Seiko Instruments Inc.
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