Datasheet

6-Channel Intelligent Fan Controller

MAX31785

MFR_NV_FAULT_LOG (DCh)

Each time the MFR_NV_FAULT_LOG command is executed, the device returns a block of 255 bytes containing one

of the 15 nonvolatile fault logs. The MFR_NV_FAULT_LOG command must be executed 15 times to dump the com-

plete nonvolatile fault log. If the returned fault log is all FFs, this indicates that this fault log has not been written by the

device. As the device is operating, it is reading the latest operating conditions for fan speed, voltage, and temperature,

and it is updating the status registers. All this information is stored in on-board RAM. When a fault is detected (if so

enabled in MFR_FAULT_RESPONSE), the device automatically logs this information to one of the 15 nonvolatile fault

logs. After 15 faults have been written, bit 0 of STATUS_CML is set and the host must clear the fault log by setting the

CLEAR_NV_FAULT_LOG bit in MFR_MODE before any additional faults are logged. All the latest status information is

logged as well as eight readings of voltage from the last 800ms in 100ms increments. If a fan is not enabled or if volt-

age or a temperature sensor is disabled, the associated fault log position returns 0000h.

There is a FAULT_LOG_COUNT (16-bit counter) at the beginning of each fault log that indicates which fault log is

the latest. This counter rolls over should more than 65,535 faults be logged. This counter is not cleared when the

CLEAR_NV_FAULT_LOG bit in MFR_MODE is toggled. The 255 bytes returned by the MFR_NV_FAULT_LOG com-

mand are described in Table 24.

If an error occurs while the device is attempting to write or clear the NV_FAULT_LOG, the device sets the CML bit in

STATUS_BYTE and STATUS_WORD; no bits are set in STATUS_CML. ALERT is asserted (if enabled in MFR_MODE).

See Figure 5.

USER NOTE: V

must be above 2.9V for the device to clear or log data into MFR_NV_FAULT_LOG.

Figure 5. MFR_NV_FAULT_LOG

FAULT LOG INDEX 0

(255 BYTES)

FAULT LOG INDEX 1

(255 BYTES)

FAULT LOG INDEX 2

(255 BYTES)

STATUS

VOLTAGE

TEMPERATURE

FAN SPEED

RAM

FLASHEACH FAULT IS WRITTEN INTO

THE NEXT FAULT LOG

EACH COMMAND READ

ACCESSES THE NEXT FAULT LOG

FAULT OCCURENCE

FAULT LOG INDEX 14

(255 BYTES)

MFR_NV_FAULT_LOG