AMC6821-Q1 Datasheet, PDF (39/54 Pages) Texas Instruments – INTELLIGENT TEMPERATURE MONITOR AND PWM FAN CONTROLLER

AMC6821-Q1
www.ti.com ...................................................................................................................................................................................................... SBAS475 – JUNE 2009
DEVICE STATUS REGISTERS
Reading the status registers clears the appropriate status bit. Status register bits are sticky (except the RTF bit).
Whenever a status bit is set, indicating an out-of-limit condition, it remains set until the event that caused it is
resolved and the status register is read. The status bit can only be cleared by reading the status register after the
event is resolved. All bits are cleared when reading the register, and all bits are reasserted if the out-of limit
condition still exists on the next monitoring cycle, unless otherwise noted.
Status Register 1 (Address 0x02, Value After Power-On or Reset = 0x00)
BIT
NAME
R/W
7
LTL
R
6
LTH
R
5
RTF
R
4
R-THERM
R
3
RTL
R
2
RTH
R
1
FANS
R
0 RPM-ALARM R
DEFAULT
0
0
0
0
0
0
0
0
DESCRIPTION
LTL = 1 when the local temperature is less than or equal to the value of the
Local-Low-Temp-Limit register. Otherwise, LTL = 0. If the local temperature is still
outside the local temperature low limit, this bit reasserts on the next monitoring cycle.
LTH = 1 when the local temperature is greater than or equal to the value of the
Local-High-Temp-Limit register. Otherwise, LTH = 0. If the local temperature is still
outside the local temperature high limit, this bit reasserts on the next monitoring cycle.
Remote sensor-failure interrupt. RTF = 1 when the remote temperature sensor fails
(short- or open-circuit). RTF = 0 when the remote sensor is in normal condition. When
RTF = 1, the OVR pin is asserted and the remote temperature data register is set to
–128°C.
RTF = 1 also generates an interrupt through the SMBALERT pin if an interrupt is
enabled (RTFIE = 1). Once RTF is set ('1'), it always remains ('1') until power-on reset or
software reset occurs, whether or not the failure condition continues. Reading the status
register does not clear the RTF bit.
Remote temperature over the remote THERM limit flag. R-THERM = 1 when the
temperature is greater than the value of the Remote-THERM-Limit register. Otherwise,
R-THERM = 0. When R-THERM = 1, the THERM pin goes low. It also generates a
THERM interrupt if THERMOVIE = 1. This bit is cleared on a read of Status Register 1.
Once cleared, this bit is not reasserted until the remote temperature falls 5°C below this
THERM limit, even if the THERM condition persists. Refer to the THERM Pin and
External Hardware Control section.
RTL = 1 when the remote temperature is less than or equal to the value of the
Remote-Low-Temp-Limit register. Otherwise, RTL = 0. If the remote temperature is still
beyond the remote temperature low limit, this bit reasserts on the next monitoring cycle.
RTH = 1 when the remote temperature is greater than or equal to the value of
Remote-High-Temp-Limit register. Otherwise, RTH = 0. If the remote temperature is still
beyond the remote temperature high limit, this bit reasserts on the next monitoring cycle.
Fan-slow flag. FANS = 1 if the TACH data are greater than or equal to the value of the
TACH-Low-Limit register. This bit indicates if the fan becomes stuck or goes under the
minimum speed. FANS = 0 if the TACH data are smaller than the TACH low limit. This
bit is cleared ('0') only after reading this register, and reasserts '1' in the next monitoring
if a fan-slow is detected. After spin-up, FANS is set ('1') even if the TACH data are less
than the TACH low limit until the register is read. FANS = 1 generates a fan out-of-range
interrupt through the SMBALERT pin if fan out-of-range is enabled (FANIE = 1). Five
consecutive fan-slow events result in a FAN FAILURE status; which asserts the
FAN-FAULT pin low. See the FAN-FAULT PIN section for details. Note that a FANS
(fan-slow) detection is not performed during spin-up.
RPM-ALARM = 1 when the TACH data are less than or equal to the value of the
TACH-High-Limit register. This means the RPM is over the maximum limit defined by the
TACH high limit. Otherwise, RPM-ALARM = 0. This bit is cleared when reading this
register. Once cleared, this bit is not reasserted on the next monitoring cycle even if the
condition still persists. This bit may be reasserted only if the RPM drops below the
allowed maximum speed. RPM-ALARM = 1 generates a fan out-of-range interrupt
through the SMBALERT pin if fan out-of-range is enabled (FANIE = 1), but does not
cause an interrupt through the FAN-FAULT pin.
Copyright © 2009, Texas Instruments Incorporated
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