SE97B_1
?NXP B.V. 2010. All rights reserved.
Product data sheet
Rev. 01 27 January 2010
9 of 53
NXP Semiconductors
SE97B
DDR memory module temp sensor with integrated SPD
7.3.2 EVENT
thresholds
7.3.2.1 Alarm window
The device provides a comparison window with an UPPER trip point and a LOWER trip
point, programmed through the Upper Boundary Alarm Trip register (02h), and Lower
Boundary Alarm Trip register (03h). The Upper Boundary Alarm Trip register holds the
upper temperature trip point, while the Lower Boundary Alarm Trip register holds the lower
temperature trip point as modified by hysteresis as programmed in the Configuration
register. When enabled, the EVENT
output triggers whenever entering or exiting (crossing
above or below) the alarm window.
" Advisory note:
NXP device: The EVENT
output can be cleared through the clear EVENT bit or
SMBus Alert Response Address (ARA).
Competitor device: The EVENT
output can be cleared only through the clear
EVENT bit.
Work-around: Only clear EVENT
output using the EVENT bit if both NXP and
competitor devices are used.
The Upper Boundary Alarm Trip should always be set above the Lower Boundary Alarm
Trip.
The alarm window limit is immediately compared with the temperature register even if it
has not been recently updated (e.g., device has been in standby) when the EVENT
is
turned on (CONFIG[3]).
Consider waiting one conversion cycle (125 ms) after setting the alarm window limit
before enabling the EVENT
output/comparing the alarm window limit with the temperature
register to ensure that there is correct data in the temperature register.
If SMBUS[2] is set, then the alarm window limit will only be compared to the Temperature
register after it has been updated when EVENT
is turned on.
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
is
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 or SMBus Alert.
The Critical Alarm Trip should always be set above the Upper Boundary Alarm Trip.
The critical trip limit is immediately compared with the temperature register even if it has
not been recently updated (e.g., device has been in standby) when the EVENT
is turned
on (CONFIG[3]).
Consider waiting one conversion cycle (125 ms) after setting the critical trip limit before
enabling the EVENT
output/comparing the critical trip limit with the temperature register to
ensure that there is correct data in the temperature register.
If SMBUS[2] is set, then the alarm window limit will only be compared to the Temperature
register after it has been updated when EVENT
is turned on.