S-34C04A Datasheet, PDF (19/22 Pages) Seiko Instruments Inc – FOR DIMM SERIAL PRESENCE DETECT

Rev.1.0_01_U
2-WIRE SERIAL E²PROM FOR DIMM SERIAL PRESENCE DETECT
S-34C04A
 Usage
1. A pull-up resistor to SDA I/O pin and SCL input pin
In consideration of I²C-bus protocol function, the SDA I/O pin and SCL input pin should be connected with a pull-up
resistor. This IC cannot transmit normally without using a pull-up resistor.
In case that the SCL input pin of this IC is connected to the Nch open-drain output pin of the master device, connect
the SCL pin with a pull-up resistor. As well, in case the SCL input pin of this IC is connected to the tri-state output pin
of the master device, connect the SCL pin with a pull-up resistor in order not to set it in "High-Z". This prevents this IC
from error caused by an uncertain output (High-Z) from the tri-state pin when resetting the master device during the
voltage drop.
2. Equivalent circuits of input pin and I/O pin
The SCL pin and the SDA pin of this IC do not have a built-in pull-down or pull-up resistor. Each of the SA0 pin, SA1
pin and SA2 pin has a built-in pull-down resistor. The SDA pin is an open-drain output. The followings are equivalent
circuits of the pins.
SCL
SDA
Figure 16 SCL Pin
SA0, SA1, SA2
Figure 17 SDA Pin
Figure 18 SA0, SA1, SA2 Pin
3. Acknowledge check
The I²C-bus protocol includes an acknowledge check function as a handshake function to prevent a communication
error. This function allows detection of a communication failure during data communication between the master
device and this IC. This function is effective to prevent malfunction, so it is recommended to perform an acknowledge
check with the master device.
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