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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

7 THERMOVIE R/W 1

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.

6 FDRC1 R/W 1 Fan driver control bit 1. Power-on default = 1. Refer to Table 15 .

5 FDRC0 R/W 0 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

4 FAN-Fault-EN R/W 1

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

3 PWMINV R/W 0

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,

2 FANIE R/W 1

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')

1 INT-EN R/W 0

disables the interrupt. Power-on default = 0.

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

0 START R/W 0 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

1 1

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

1 0

temperature. Power-on default mode.

0 0 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

0 1 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.

Product Folder Link(s): AMC6821