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DEVICE CONFIGURATION REGISTERS

AMC6821

SBAS386C – MAY 2006 – REVISED JULY 2007

In this section, all interrupts are the interrupt signal through the SMBALERT pin, unless otherwise noted.

Configuration Register 1 (Address 0x00, Value After Power-On Reset = 0xD4)

BIT

NAME

R/W

DEFAULT

DESCRIPTION

THERM interrupt enable. When this bit is set, the THERM interrupt is enabled.

L-THERM = 1 or R-THERM = 1 causes an interrupt. When this bit is cleared ('0'), the

THERMOVIE

R/W

THERM interrupt is disabled. When disabled, L-THERM = 1 or R-THERM = 1 does not

assert the SMBALERT pin, but forces the THERM pin low. Power-on default = 1.

FDRC1

R/W

Fan driver control bit 1. Power-on default = 1. Refer to Table 15.

FDRC0

R/W

Fan driver control bit 0. Power-on default = 0. Refer to Table 15.

Setting this pin to '1' enables the FAN-FAULT pin. Clearing this pin ('0') disables the

FAN-Fault-EN

R/W

FAN-FAULT pin (always in Hi-Z). Power-on default = 1.

PWM invert bit. When PWMINV = 0 (default), the PWM-Out pin goes low for 100% duty

cycle (suitable for driving the fan using a PMOS device). Setting PWMINV to '1' makes

PWMINV

R/W

the PWM-Out pin go high (with an external pull-up resistor) for 100% duty cycle (suitable

for driving the fan using a NMOS device). Power-on default = 0.

Fan RPM interrupt enable bit. Power-on default = 1. When FANIE = 1, the FAN-RPM

interrupt is enabled. FANS = 1 or RPM-ALARM = 1 generates a FANORN interrupt,

FANIE

R/W

making the SMBALERT pin go low. When FANIE = 0, a FAN-RPM interrupt is disabled.

Fan out-of-range = 1 does not generate an interrupt.

Setting this bit to '1' enables the interrupt from the SMBALERT pin. Clearing this bit ('0')

INT-EN

R/W

disables the interrupt. Power-on default = 0.

Temperature monitoring and fan speed monitoring. When START = 0 , only

START

R/W

software-DCY control mode works; software-RPM and auto temperature control modes

do not work.

Table 15. Fan Driver Control Bits

FDRC1

FDRC0

FUNCTION

Maximum speed calculated control. The required duty cycle for remote temperature and

local temperature is calculated respectively. The larger value is used to control the fan.

Auto remote-temperature-fan control. The PWM duty cycle is controlled by the remote

temperature. Power-on default mode.

Software DCY control. Host writes DCY register to set the PWM duty cycle directly.

Software RPM control. Host writes the TACH setting register with the value corresponding

to the desired RPM. The device measures the actual RPM and adjusts the PWM duty cycle

to maintain the fan speed to the target value.

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