SE98A Datasheet, PDF (5/43 Pages) NXP Semiconductors – DDR memory module temp sensor, 1.7 V to 3.6 V

NXP Semiconductors
SE98A
DDR memory module temp sensor, 1.7 V to 3.6 V
7. Functional description
7.1 Serial bus interface
The SE98A uses the 2-wire serial bus (I²C-bus/SMBus) to communicate with a host
controller. The serial bus consists of a clock (SCL) and data (SDA) signals. The device
can operate on either the I²C-bus Standard/Fast mode or SMBus. The I²C-bus
Standard-mode is defined to have bus speeds from 0 Hz to 100 kHz, I²C-bus Fast-mode
from 0 Hz to 400 kHz, and the SMBus is from 10 kHz to 100 kHz. The host or bus master
generates the SCL signal, and the SE98A uses the SCL signal to receive or send data on
the SDA line. Data transfer is serial, bidirectional, and is one bit at a time with the Most
Significant Bit (MSB) transferred first, and a complete I²C-bus data is 1 byte. Since SCL
and SDA are open-drain, pull-up resistors must be installed on these pins.
7.2 Slave address
The SE98A uses a 4-bit fixed and 3-bit programmable (A0, A1 and A2) 7-bit slave address
that allows a total of eight devices to coexist on the same bus. The input of each pin is
sampled at the start of each I²C-bus/SMBus access. The A0, A1 and A2 pins are pulled
LOW internally. The A0 pin is also overvoltage tolerant, supporting 10 V software write
protection when applied to the SPD that shares common address lines.
Fig 5. Slave address
MSB
00
slave address
R/W
LSB
1 1 A2 A1 A0 X
fixed
hardware
selectable
002aab304
SE98A_2
Product data sheet
Rev. 02 — 6 August 2009
© NXP B.V. 2009. All rights reserved.
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