se98pw NXP Semiconductors, se98pw Datasheet - Page 8

• Manufacturer Part Number: se98pw
• Description: Se98 So-dimm Smbus/i2c-bus Temperature Sensor
• Manufacturer: NXP Semiconductors

NXP Semiconductors
SE98_2
Product data sheet
Fig 6. How SE98 responds to SMBus Alert
SMBus ALERT
host detects
7.8 SMBus Alert
7.9 SMBus/I
START bit
The SE98 supports SMBus Alert when it is programmed for the Interrupt mode and when
the EVENT polarity bit is set to logic 0. The EVENT pin can be ANDed with other EVENT
or ALERT signals from other slave devices to signal their intention to communicate with
the host controller. When the host detects EVENT or ALERT signal LOW, it issues an
Alert Response Address (ARA) to which a slave device would respond with its address.
When there are multiple slave devices generating an Alert the SE98 performs bus
arbitration. If it wins the bus, it responds to the ARA and then clears the EVENT pin.
Remark: Either in comparator mode or when the SE98 crosses the critical temperature,
the host must also read the EVENT status bit and provide remedy to the situation by
bringing the temperature to within the alarm window or below the critical temperature if
that bit is set. Otherwise, the EVENT pin will not get de-asserted.
The data registers in this device are selected by the Pointer register. At power-up, the
Pointer register is set to ‘00’, the location for the Capability register. The Pointer register
latches the last location it was set to. Each data register falls into one of three types of
user accessibility:
A ‘write’ to this device will always include the address byte and the pointer byte. A write to
any register other than the Pointer register requires two data bytes.
Reading this device can take place either of two ways:
S
•
•
•
•
•
Read only
Write only
Write/Read same address.
If the location latched in the Pointer register is correct (most of the time it is expected
that the Pointer register will point to one of the Temperature register (as it will be the
data most frequently read), then the read can simply consist of an address byte,
followed by retrieving the two data bytes.
If the Pointer register needs to be set, then an address byte, pointer byte,
repeat START, and another address byte will accomplish a read.
0
0
master sends a START bit,
ARA and a read command
Alert Response Address
2
C-bus interface
0
1
1
Rev. 02 — 7 January 2008
0
0
read
1
acknowledge
0
0
SO-DIMM SMBus/I
The last bit of slave address
Slave acknowledges and
sends its slave address.
0
is hard coded '0'.
1
device address
1
A2
A1
not acknowledge
2
C-bus temperature sensor
A0
0
sends a STOP bit
host NACK and
1
© NXP B.V. 2008. All rights reserved.
002aab330
STOP bit
P
SE98
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