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StatusRegisterRead

THERMLimit

Temperature

THERM

INT

SMBALERT

via

INT

SMBALERT

via

5°

AMC6821

SBAS386C – MAY 2006 – REVISED JULY 2007

When the THERM limit is exceeded, the corresponding status flag bit (R-THERM or L-THERM of Status Register

1 or Status Register 2) is set to '1', and the THERM interrupt through the SMBALERT pin is generated if it is

enabled (THERMOVIE of bit Configuration Register 1 is set to '1'). This interrupt forces the SMBALERT pin low.

Note that the THERM pin is always forced to low when R-THERM = 1 or L-THERM = 1, no matter what the

status of THERMOVIE is. Reading the status registers clears the flag bit (R-THERM and L-THERM). Clearing the

flag bit makes the SMBALERT pin go back to high, but does not negate the THERM pin. It remains low until the

temperature falls 5C below the exceeded THERM limit. After this bit is cleared, the active flag bit (R-THERM for

remote temperature or L-THERM for local temperature) and the THERM interrupt are not re-armed until the

temperature falls 5

°C below the exceeded THERM limit. This procedure is shown in Figure 23.

Figure 23. Operation of the THERM Interrupt and the THERM Pin

When working as an output, the status of the THERM pin affects the RPM fan. If the THERM-FAN-EN bit is set

('1'), the fan goes to full-speed (that is, the duty cycle is 100%) when the THERM pin goes low. However, when

THERM-FAN-EN = 0, the status of the THERM pin does not affect the fan speed.

THERM Pin As An Input

When this pin works as input, it is the input of the external hardware control signal; the THERM-IN bit of Status

driven at full speed (that is, the duty cycle is 100%), no matter what THERM-FAN-EN is. The THERM-FAN-EN

bit has no effect when the THERM pin works as an input.

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