SE97 Datasheet, PDF (6/54 Pages) NXP Semiconductors – DDR memory module temp sensor with integrated SPD, 3.3 V

NXP Semiconductors
SE97
DDR memory module temp sensor with integrated SPD, 3.3 V
7. Functional description
7.1 Serial bus interface
The SE97 communicates with a host controller by means of the 2-wire serial bus
(I²C-bus/SMBus) that consists of a serial clock (SCL) and serial data (SDA) signals. The
device supports SMBus, I²C-bus Standard-mode and Fast-mode. The I²C-bus standard
speed is defined to have bus speeds from 0 Hz to 100 kHz, I²C-bus fast speed 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 SE97 uses the SCL signal to receive or send data on the SDA
line. Data transfer is serial, bidirectional, and is one byte at a time with the Most Significant
Bit (MSB) is transferred first. Since SCL and SDA are open-drain, pull-up resistors must
be installed on these pins.
7.2 Slave address
The SE97 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 co-exist on the same bus. The A0, A1 and A2 pins
are pulled LOW internally. The A0 pin is also overvoltage tolerant supporting 10 V
software write protect. When it is driven higher than 7.8 V, writing a special command
would put the EEPROM in reversible write protect mode (see Section 7.10.2 “Memory
protection”). Each pin is sampled at the start of each I²C-bus/SMBus access. The
temperature sensor’s fixed address is ‘0011b’. The EEPROM’s fixed address for the
normal EEPROM read/write is ‘1010b’, and for EEPROM software protection command is
‘0110b’. Refer to Figure 6.
MSB
00
slave address
R/W
LSB
1 1 A2 A1 A0 X
fixed
hardware
selectable
002aab304
a. Temperature sensor
Fig 6. Slave address
MSB
10
slave address
R/W
LSB
1 0 A2 A1 A0 X
fixed
hardware
selectable
002aab351
b. EEPROM (normal read/write)
MSB
01
slave address
R/W
LSB
1 0 A2 A1 A0 X
fixed
hardware
selectable
002aab352
c. EEPROM (software
protection command)
SE97_5
Product data sheet
Rev. 05 — 6 August 2009
© NXP B.V. 2009. All rights reserved.
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