ADM1024 datasheet(21/28 Pages) AD

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ADM1024

–21–

REV. 0

USING THE CONFIGURATION REGISTERS

Control of the ADM1024 is provided through two conﬁguration

registers. The ADC is stopped upon power-up, and the

INT_Clear

signal is asserted, clearing the

INT output. The Conﬁguration

Registers are used to start and stop the ADM1024; enable or dis-

able interrupt outputs and modes, and provide the initialization

function described above.

Bit 0 of Conﬁguration Register 1 controls the monitoring loop

of the ADM1024. Setting Bit 0 low stops the monitoring loop

and puts the ADM1024 into a low power mode thereby reducing

power consumption. Serial bus communication is still possible

with any register in the ADM1024 while in low-power mode.

Setting Bit 0 high starts the monitoring loop.

Bit 1 of Conﬁguration Register 1 enables or disables the

INT

Interrupt output. Setting Bit 1 high enables the

INT output,

setting Bit 1 low disables the output.

Bit 2 of Conﬁguration Register 1 enables or disables the

THERM

output. Setting Bit 1 high enables the

INT output, setting Bit 1

low disables the output.

Bit 3 of Conﬁguration Register 1 is used to clear the

INT inter-

rupt output when set high. The ADM1024 monitoring function

will stop until Bit 3 is set low. Interrupt Status register contents

will not be affected.

Bit 4 of Conﬁguration Register 1 causes a low-going 45 ms (typ)

pulse at the

RESET pin (Pin 12).

Bit 6 of Conﬁguration Register 1 is used to clear an interrupt at

the

THERM output when it is set to 1.

Bit 7 of Conﬁguration Register 1 is used to start a Conﬁguration

Bit 0 of Conﬁguration Register 2 is used to mask temperature

interrupts at the

INT output when it is set to 1. The THERM

output is unaffected by this bit.

Bits 1 and 2 of Conﬁguration Register 2 lock the values stored

in the Local and Remote Fan Control Registers at addresses 13h

and 14h. The values in these registers cannot be changed until a

power-on reset is performed.

Bit 3 of Conﬁguration Register 2 selects the

THERM interrupt

mode. The default value of 0 selects one-time mode. Setting this

bit to 1 selects ACPI mode.

STARTING CONVERSION

The monitoring function (analog inputs, temperature, and fan

speeds) in the ADM1024 is started by writing to Conﬁguration

INT_Enable (Bit

1) should be set to 1, and

INT Clear (Bit 3) set to 0 to enable

interrupts. The

THERM enable bit (Bit 2) should be set to 1

and the

THERM Clear bit (Bit 6) should be set to 0 to enable

temperature interrupts at the

THERM pin. Apart from initially

starting together, the analog measurements and fan speed mea-

surements proceed independently, and are not synchronized in

any way.

The time taken to complete the analog measurements depends

on how they are conﬁgured, as described elsewhere. The time

taken to complete the fan speed measurements depends on the

fan speed and the number of tach output pulses per revolution.

Once the measurements have been completed, the results can be

read from the Value Registers at any time.

REDUCED POWER AND SHUTDOWN MODE

The ADM1024 can be placed in a low-power mode by setting

Bit 0 of the Conﬁguration Register to 0. This disables the inter-

nal ADC. Full shutdown mode may then be achieved by setting

Bit 0 of the Test Register to 1. This turns off the analog output

and stops the monitoring cycle, if running, but it does not affect

the condition of any of the registers. The device will return to its

previous state when this bit is reset to zero.

APPLICATION CIRCUIT

Figure 25 shows a generic application circuit using the ADM1024.

The analog monitoring inputs are connected to the power

supplies including two processor core voltage inputs. The VID

inputs are connected to the processor voltage ID pins. There are

two tach inputs from fans, and the analog output is used to control

the speed of a third fan. An opto-sensor for chassis intrusion

detection is connected to the CI input. Of course, in an actual

application, every input and output may not be used, in which

case unused analog and digital inputs should be tied to analog

or digital ground as appropriate.

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