EMC2101-R-ACZL-TR datasheet(13/56 Pages) MICROCHIP

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DS20006703A-page 13

EMC2101

4.1

Modes of Operation (EMC2101-R

Only)

The EMC2101-R has two modes of operation based on

the pull-up resistor on the ALERT pin (see Table 4-1).

The modes of operation are:

Host Configuration Mode: an SMBus Host

configures the EMC2101-R upon startup to

allow for polling for temperature or fan

information or the user can use the ALERT pin

interrupt to determine which action is required.

Automatic Configuration Mode: the EMC2101-R

queries an SMBus compatible EEPROM

located at a known address (see Section 2.9

“Programming from EEPROM”) and automat-

ically loads its registers with the contents of the

EEPROM. This mode does not require host

intervention but a host can poll the device for

temperature and fan information.

4.2

Power Up (EMC2101-R Only)

The EMC2101-R (only) will power up with the fan driver

set to either 100% duty cycle or 0% duty cycle, depend-

ing on the value of the pull-up resistor on the

ALERT/TACH pin. (See Table 4-1.) It will remain in this

state until either the Fan Setting Register is written or

until the following activities have occurred:

The Fan Control Look-Up Table is loaded and

the PROG bit is set to ‘0’ .

The temperature monitoring block performs its

first comparison against the Look-Up Table.

If the Fan Control Look-Up Table is used, the

EMC2101-R Fan Driver will be immediately set to the

appropriate setting in the table based on the measured

temperature.

4.3

Power Modes

The EMC2101 supports multiple power modes that are

user configurable. The temperature monitoring and fan

control functions of the device are independent. The

power modes are:

Normal. The temperature monitoring and fan

driver circuits are both active. The device

updates all temperature channels at the user

programmed

conversion

rate

(see

updated, the limits are checked and the fan

driver is updated based on the values in the Fan

Control Look-Up Table (if the Fan Control

Look-Up Table is enabled).

Standby. The temperature monitoring and fan

driver circuits are both disabled. The device will

not update temperature data automatically and

the fan output will be set to default drive. A

one-shot command can be issued that will

refresh the temperature data. The limits are only

checked when the temperature data is updated.

Mixed. The temperature monitoring block is dis-

abled, but the fan driver block is active. The

device will not update temperature data auto-

matically and the fan driver output will not be

updated automatically based on temperature. A

one-shot command can be issued that will

refresh the temperature data and update the fan

driver based on the values in the Fan Control

Look-Up Table (if the Fan Control Look-Up Table

is enabled).

4.4

ALERT/TACH Output

The ALERT/TACH pin (Pin 6) is an open drain output

and requires a pull-up resistor to VDD when configured

as an ALERT output.

When configured as a TACH input, the ALERT/TACH

pin will not function as an ALERT output. Error condi-

tions will not trigger an interrupt (though will be updated

in the Status Registers as normal) and the MASK bits

will do nothing. Likewise, the device will not respond to

the ARA command.

For the EMC2101-R, the value of this pull-up resistor

determines the initial FAN output mode of operation as

well as whether the device auto loads from an

EEPROM or via an SMBus host per Table 4-1.

After power-up, the EMC2101-R requires 10 ms to

initialize and determine the operating mode.

When configured as an interrupt, the ALERT/TACH pin

is maskable for each alert condition. If the

ALERT/TACH pin is masked, then it will not respond to

the corresponding condition (though the Alert Status

functions described below and is controlled by

ALERT_COMP bit (bit 0) in the Averaging Filter

TABLE 4-1:

ALERT/TACH PULL-UP RESISTORS SMBus/FAN MODE FOR EMC2101-R

ALERT/TACH

Pull-up Resistor

SMBus Mode

FAN Mode

Polarity Bit Setting

(See Section 5.16, Fan

Configuration

5.6 kΩ ±5%

Host Load via SMBus

FAN output initialize to 100% Duty Cycle

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