se98a NXP Semiconductors, se98a Datasheet - Page 11

• Manufacturer Part Number: se98a
• Description: Ddr Memory Module Temp Sensor, 1.7 V To 3.6 V
• Manufacturer: NXP Semiconductors

NXP Semiconductors
SE98A_1
Product data sheet
7.6 Device initialization
7.7 SMBus Time-out
7.8 SMBus ALERT
SE98A temperature sensors have programmable registers, which, upon power-up, default
to zero. The open-drain EVENT output is default to being disabled, comparator mode and
active LOW. The alarm trigger registers default to being unprotected. The configuration
registers, upper and lower alarm boundary registers and critical temperature window are
defaulted to zero and need to be programmed to the desired values. SMBus TIMEOUT
feature defaults to being enabled and can be programmed to disable. These registers are
required to be initialized before the device can properly function. Except for the SPD,
which does not have any programmable registers, and does not need to be initialized.
Table 4
registers.
Table 4.
The SE98A supports the SMBus time-out feature. If the host holds SCL LOW between
25 ms and 35 ms, the SE98A would reset its internal state machine to the bus idle state to
prevent the system bus hang-up. This feature is turned on by default. The SMBus time-out
is disabled by writing a logic 1 to bit 7 of register 22h.
Remark: When SMBus time-out is enabled, the I
the SMBus time-out timer, and goes down to only 10 kHz.
The SE98A has no SCL driver, so it cannot hold the SCL line LOW.
The SE98A 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 SE98A
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 SE98A 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.
Register
01h
02h
03h
04h
22h
shows the default values and the example value to be programmed to these
Registers to be initialized
Default value
0000h
0000h
0000h
0000h
0000h
Rev. 01 — 5 March 2009
Example value
0209h
0550h
1F40h
05F0h
0000h
DDR memory module temp sensor, 1.7 V to 3.6 V
Description
Configuration register
Upper Boundary Alarm Trip register = 85 C
Lower Boundary Alarm Trip register = 20 C
Critical Alarm Trip register = 95 C
SMBus register = no change
•
•
•
2
C-bus minimum bus speed is limited by
hysteresis = 1.5 C
EVENT output = Interrupt mode
EVENT output is enabled
© NXP B.V. 2009. All rights reserved.
SE98A
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