SE98ATP datasheet(11/43 Pages) NXP

11 / 43 page

SE98A_4

Product data sheet

Rev. 04 — 25 November 2009

11 of 43

NXP Semiconductors

SE98A

DDR memory module temp sensor, 1.7 V to 3.6 V

7.5 Power-up default condition

After power-on, the SE98A is initialized to the following default condition:

• Starts monitoring local sensor

• EVENT register is cleared—EVENT output is pulled HIGH by external pull-ups

• EVENT hysteresis is defaulted to 0 °C

• Command pointer is defaulted to ‘00h’

• Critical Temp, Alarm Temperature Upper and Lower Boundary Trip register are

defaulted to 0

°C

• Capability register is defaulted to ‘0037h’ for the B-grade and VHV capability

• Operational mode: comparator

• SMBus register is defaulted to ‘00h’

7.6 Device initialization

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 shows the default values and the example value to be programmed to these

registers.

Table 4.

Registers to be initialized

Default value

Example value

Description

01h

0000h

0209h

Configuration register

• hysteresis = 1.5 °C

• EVENT output = Interrupt mode

• EVENT output is enabled

02h

0000h

0550h

Upper Boundary Alarm Trip register = 85

°C

03h

0000h

1F40h

Lower Boundary Alarm Trip register =

−20 °C

04h

0000h

05F0h

Critical Alarm Trip register = 95

°C

22h

0000h

SMBus register = no change

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