Datasheet

6-Channel Intelligent Fan Controller

MAX31785

CLEAR_FAULTS (03h)

The CLEAR_FAULTS command is used to clear any fault or warning bits in the status registers that have been set. This

command clears all bits simultaneously. If a fault is still present after the CLEAR_FAULTS command is executed, the

fault status bit is set again and the host is also notified by asserting ALERT (if enabled in MFR_MODE). This command

is write-only. There is no data byte for this command.

WRITE_PROTECT (10h)

The WRITE_PROTECT command is used to provide protection against accidental changes to the device operating

memory. All supported commands can have their parameters read, regardless of the WRITE_PROTECT settings. The

WRITE_PROTECT message content is described in Table 10.

Table 10. WRITE_PROTECT Command Byte

Note: No fault or error is generated if the host attempts to write to a protected area.

STORE_DEFAULT_ALL (11h)

The STORE_DEFAULT_ALL command instructs the device to transfer the device configuration information to the

internal flash memory array. Not all information is stored. Only configuration data is stored, not any status or opera-

tional data. If an error occurs during the transfer, ALERT asserts if enabled and the CML bit in STATUS_BYTE and

STATUS_WORD is set to 1. No bits are set in STATUS_CML. It is NOT recommended to use the STORE_DEFAULT_ALL

command while the device is operating fans. The device is unresponsive to PMBus commands and does not monitor

fans while transferring the configuration. After this command is sent, another command should not be sent for at least

250ms. This command is write-only. There is no data byte for this command.

USER NOTE: V

must be above 2.9V for the device to perform the STORE_DEFAULT_ALL command.

RESTORE_DEFAULT_ALL (12h)

The RESTORE_DEFAULT_ALL command transfers the default configuration information from the internal flash memory

array to the user memory registers in the device. The RESTORE_DEFAULT_ALL command should only be executed

when the device is not operating the fans. Upon a device reset, this command is automatically executed by the device

without PMBus action required. After this command is sent, another command should not be sent for at least 250ms.

This command is write-only. There is no data byte for this command.

CAPABILITY (19h)

The CAPABILITY command is used to determine some key capabilities of the device. The CAPABILITY command is

read-only. The message content is described in Table 11.

Table 11. CAPABILITY Command Byte

COMMAND BYTE MEANING

80h Disable all writes except the WRITE_PROTECT command.

40h Disable all writes except the WRITE_PROTECT and PAGE commands.

00h Enable writes for all commands (default).

BIT DESCRIPTION MEANING

7 Packet-Error Checking 0 = PEC not supported.

6:5 PMBus Speed 00 = Maximum supported bus speed is 100kHz.

4 ALERT

1 = Device supports an ALERT output (if ALERT is enabled in MFR_MODE).

0 = Device does not support ALERT output (ALERT is disabled in MFR_MODE).

3:0 Reserved Always returns 0000.