AMC6821 Datasheet, PDF (35/47 Pages) Burr-Brown (TI) – Analog Monitor and Control Circuit

AMC6821
www.ti.com
SBAS386A – MAY 2006 – REVISED MAY 2006
Status Register 2 (Address 0x03, Value After Power-On or Reset = 0x00)
BIT
NAME
R/W DEFAULT DESCRIPTION
7
THERM-IN
R
0
Status of the THERM pin as an input. When this input is pulled low, THERM-IN = 1, and
the fan is driven at full speed. This bit is cleared when reading this register.
6
L-THERM
R
Local temperature over the local THERM limit flag. L-THERM = 1 when the local
temperature is greater than the value of the Local-THERM-Limit register. Otherwise,
L-THERM = 0. When L-THERM = 1, the THERM pin goes low. It also generates a
0
THERM interrupt through the SMBALERT pin, if enabled (THERMOVIE = 1). This bit is
cleared on a read of Status Register 1. Once cleared, this bit is not reasserted until the
temperature falls 5°C below the THERM limit, even if the THERM condition persists.
Refer to the THERM Pin and External Hardware Control section.
5
LPSV
R
Active control temperature below the PSV (passive cooling) temperature flag. This bit is
set to '1' when the active control temperature is equal to or below the PSV temperature.
0
Otherwise, this bit is cleared ('0'). LPSV = 1 generates a PSV interrupt on the
SMBALERT pin, if enabled (PSVIE = 1). This bit is cleared when reading this register. If
the active control temperature remains equal to or below the PSV temperature, this bit
reasserts on the next monitoring cycle.
4
LTC
R
Local temperature over the local critical temperature flag. This bit is set ('1') when the
local temperature is equal to or above the local critical temperature. LTC = 0 if the local
0
critical temperature is below this value. LTC = 1 asserts the OVR pin low and generates
an LTC interrupt (non-maskable) though the SMBALERT pin. This bit is cleared when
reading this register. If the over-critical limit condition persists, this bit reasserts on the
next monitoring cycle.
3
RTC
R
Remote temperature over the remote critical temperature flag. This bit is set to '1' when
the remote temperature is equal to or above the remote critical temperature. RTC = 0 if
0
the remote critical temperature is below this value. RTC = 1 asserts the OVR pin low
and generates an RTC interrupt (non-maskable) though the SMBALERT pin. This bit is
cleared when reading this register. If the over-critical limit condition persists, this bit
reasserts on next monitoring cycle.
2
Reserved
R
0
Reserved. Reading returns '0'.
1
Reserved
R
0
Reserved. Reading returns '0'.
0
Reserved
R
0
Reserved. Reading returns '0'.
FAN CONTROLLER REGISTERS
DCY (Duty Cycle) Register (Address 0x22, Value After Power-On or Reset = 0x55)
BIT
7 (MSB)
6
5
4
3
2
1
0
NAME
DCY7 (MSB)
DCY6
DCY5
DCY4
DCY3
DCY2
DCY1
DCY0
DEFAULT
0
1
0
1
0
1
0
1
DESCRIPTION
DCY CODE
DUTY CYCLE
0x00
0%
0x01
0.392%
... ...
... ...
0x40
25%
... ...
... ...
0x80
50%
... ...
... ...
0xFF
100%
The DCY register stores the value of the PWM duty cycle, 0x00 corresponds to 0%, and 0xFF to 100%. 1LSB
corresponds to 0.392%. Power-on default = 0x55, 33.2%.
In reading operation, the returned data are the actual duty cycle (DCY) value driving the PWM-Out pin. In writing
operation, the data written is the actual DCY driving the PWM-Out pin in the software DCY control mode.
However, in all other control modes, the data being written are not used to drive the PWM. Instead, it is stored in
a temporary register, and controls the PWM immediately after the control mode is changed to the software DCY
control mode.
Submit Documentation Feedback
35