SE97 Datasheet, PDF (10/54 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
– 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 µs.
5. Read Event value.
– SE97B will compare alarm window and temperature register immediately.
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 (CEVNT) in the
configuration register de-asserts the EVENT output until the next trigger condition occurs.
In interrupt mode, EVENT asserts when the temperature crosses the alarm upper
boundary. If the EVENT output is cleared and the temperature continues to increase until
it crosses the critical temperature threshold, EVENT asserts again. Because the
temperature is greater than the critical temperature threshold, a Clear EVENT command
does not clear the EVENT output. Once the temperature drops below the critical
temperature, EVENT de-asserts immediately.
• Advisory note:
– NXP device: If the EVENT output is not cleared before the temperature goes above
the critical temperature threshold EVENT de-asserts immediately when
temperature drops below the critical temperature.
– Competitor devices: If the EVENT output is not cleared before or when the
temperature is in the critical temperature threshold, EVENT will remain asserted
after the temperature drops below the critical temperature until a Clear EVENT
command.
SE97_5
Product data sheet
Rev. 05 — 6 August 2009
© NXP B.V. 2009. All rights reserved.
10 of 54