SE98ATP,547【PDF 9/43 页】IC TEMP SENSOR DDR 8-HWSON

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Sheet目录46

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SE98A_4

Product data sheet

Rev. 04 25 November 2009

9 of 43

NXP Semiconductors

SE98A

DDR memory module temp sensor, 1.7 V to 3.6 V

7.3.2.2 Critical trip

The T

th(crit)

temperature setting is programmed in the Critical Alarm Trip register (04h) as

modified by hysteresis as programmed in the Configuration register. When the

temperature reaches the critical temperature value in this register (and EVENT

enabled), the EVENT

output asserts and cannot be de-asserted until the temperature

drops below the critical temperature threshold. The EVENT

cannot be cleared through the

Clear EVENT

bit (CEVNT) or SMBus ALERT.

The Critical Alarm Trip should always be set above the Upper Boundary Alarm Trip.

" Advisory notification:

NXP device: Requires one conversion cycle (125 ms) after setting the Alarm

Window before comparing the alarm limit with temperature register to ensure that

there is correct data in the temperature register before comparing with the Alarm

Window and operating EVENT

output.

Competitor devices: Compares the Alarm Window with temperature register at any

time, so they get the EVENT

output immediately when new T

th(crit)

and

EVENT

output are set at the same time.

Work-around: Wait at least 125 ms before enabling EVENT

output (EOCTL = 1).

Intel will change Nehalem BIOS so that T

th(crit)

is set for more than 125 ms before

EVENT

output is enabled and Event value is checked.

1. Set T

th(crit)

2. Doing something else (make sure that exceeds 125 ms).

3. Enable the EVENT

output (EOCTL = 1).

4. Wait 20 約.

5. Read Event value.

SE98B will compare Alarm Window and temperature register immediately after

setting.

7.3.3 Event operation modes

7.3.3.1 Comparator mode

In comparator mode, the EVENT

output behaves like a window-comparator output that

asserts when the temperature is outside the window (e.g., above the value programmed in

the Upper Boundary Alarm Trip register or below the value programmed in the Lower

Boundary Alarm Trip register or above the Critical Alarm Trip resister if T

th(crit)

only is

selected). Reads/writes on the registers do not affect the EVENT

output in comparator

mode. The EVENT

signal remains asserted until the temperature goes inside the alarm

window or the window thresholds are reprogrammed so that the current temperature is

within the alarm window.

The comparator mode is useful for thermostat-type applications, such as turning on a

cooling fan or triggering a system shutdown when the temperature exceeds a safe

operating range.

7.3.3.2 Interrupt mode

In interrupt mode, EVENT

asserts whenever the temperature crosses an alarm window

threshold. After such an event occurs, writing a 1 to the Clear EVENT

bit in the

configuration register de-asserts the EVENT

output until the next trigger condition occurs.

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