Datasheet

LTC2974
71
2974fc
For more information www.linear.com/LTC2974
pMbus coMManD DescripTion
MFR_FAULT_LOG_CLEAR
This command initializes the EEPROM block reserved for fault logging. Any previous fault log stored in EEPROM will
be erased by this operation and logging of the fault log RAM to EEPROM will be enabled. Make sure that Mfr_fault_
log_status_ram = 0 before issuing the MFR_FAULT_LOG_CLEAR command.
MFR_FAULT_LOG_STATUS
This register is used to manage fault log events. The Mfr_fault_log_status_eeprom bit is set after a MFR_FAULT_LOG_
STORE command or a faulted-off event triggers a transfer of the fault log from RAM to EEPROM. This bit is cleared
by a MFR_FAULT_LOG_CLEAR command.
Mfr_fault_log_status_ram is set after a MFR_FAULT_ LOG_RESTORE to indicate that the data in the RAM has been
restored from EEPROM and not yet read using a MFR_FAULT_LOG command. This bit is cleared only by a successful
execution of an MFR_FAULT_LOG command.
MFR_FAULT_LOG_STATUS Data Contents
BIT(S) SYMBOL OPERATION
b[7:2] Reserved Read only, always returns 0s.
b[1] Mfr_fault_log_status_ram Fault log RAM status:
0: The fault log RAM allows updates.
1: The fault log RAM is locked until the next MFR_FAULT_LOG read.
b[0] Mfr_fault_log_status_eeprom Fault log EEPROM status:
0: The transfer of the fault log RAM to the EEPROM is enabled.
1: The transfer of the fault log RAM to the EEPROM is inhibited.
MFR_FAULT_LOG
Read only. This 2040-bit (255 byte) data block contains a copy of the RAM buffer fault log. The RAM buffer is continu-
ously updated after each ADC conversion as long as Mfr_fault_log_status_ram is clear.
With
Mfr_config_all_fault_log_enable = 1
and Mfr_fault_log_status_eeprom = 0, the RAM buffer is transferred to EE-
PROM whenever an LTC2974 fault causes a channel to latch off or a MFR_FAULT_LOG_STORE command is received.
This transfer is delayed until the ADC has updated its READ values for all channels when Mfr_config_all_fast_fault_log
is clear
, otherwise it happens within 24ms. This optional delay can be used to ensure that the slower ADC monitored
values are all updated for the case where a fast supervisor detected fault initiates the transfer to EEPROM.
Mfr_fault_log_status_eeprom is set high after the RAM buffer is transferred to EEPROM and not cleared until a
MFR_F
AULT_LOG_CLEAR is received, even if the LTC2974 is reset or powered down. Fault log EEPROM transfers are
not initiated as a result of Status_mfr_discharge events.
During a MFR_FAULT_LOG read, data is returned one byte at a time as defined in Table 2. The fault log data is parti
-
tioned into two sections. The first section is referred to as the preamble and contains the Position_last pointer, time
information and peak and min values. The second section contains a chronological record of telemetr
y and requires
Position_last for proper interpretation. The fault log stores approximately 300ms of telemetry. T
o prevent timeouts
during block reads, it is recommended that Mfr_config_all_longer_pmbus_timeout be set to 1.