ADP1055ACPZ-R7 datasheet(43/140 Pages) AD

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Data Sheet

ADP1055

Rev. A | Page 43 of 140

BLACK BOX FEATURE

BLACK BOX OPERATION

The ADP1055 supports a configurable black box feature. Using

this feature, the device records to the EEPROM vital data about

the faults that cause the system to shut down. Two dedicated

EEPROM pages are used for this purpose: Page 2 and Page 3.

When the ADP1055 encounters a fault with the action to shut

down the device, a snapshot of the current telemetry is taken, as

well as the first fault that caused the shutdown (see Figure 68).

If the black box feature is enabled, this information is saved to

the EEPROM before the device shuts down.

Figure 68. Black Box Write Operation

This black box feature is extremely helpful in troubleshooting a

failed system during testing and evaluation. If a system is recalled

for failure analysis, it is possible to read this information from

the EEPROM to help investigate the root cause of the failure.

Only a limited number of writes to the EEPROM are allowed.

Using Register 0xFE48[1:0], the user can set the level of infor-

mation that is logged in the black box, as follows:



No recording.



Only record telemetry just before the final shutdown.



Record telemetry of final shutdown and all intermittent

retry attempts (if device is set to shut down and retry).



Record telemetry of final shutdown, all retry attempts, and

normal power-down operations using the CTRL pin or the

OPERATION command.

Using Register 0xFE48[2], the user can program the maximum

number of records to 158,000 (recommended when the ambient

temperature of the ADP1055 is less than 85°C) or to 16,000

(when the ambient temperature of the ADP1055 is less than

125°C). If the number of records exceeds the programmed

value, the recording of data to the EEPROM is halted and the

STATUS_CML bit (Register 0x7E[0]) is set and remains set.

Data accumulated after the limit is reached is not reliable and

should be ignored.

If a device experiences multiple concurrent faults, the ID of the

first fault that triggers the system to shut down is captured in

the FIRST_FAULT_ID register (Register 0xFE95). The FFID

and all flag status and telemetry data are captured in the black

box at every write to the black box (see the Black Box Contents

section for a list of the data saved). The last valid byte of each

record is a PEC byte, which is used to calculate the validity of

each record stored in the EEPROM.

Following each recording, the record number (Rec_No) is

incremented, and this number is compared to the maximum

allowed number of records. If Rec_No equals the maximum

record number (158,000 or 16,000), no additional black box

recording is allowed because the EEPROM has reached its

maximum allowed erase program cycles and any additional

recording is unreliable.

BLACK BOX CONTENTS

Page 2 and Page 3 of the EEPROM are reserved for black box

operation. The size of each EEPROM page is 512 bytes; each

page is composed of eight records with 64 bytes each. Page 2

and Page 3 combined give a total of 16 records, which function

as a circular buffer for recording black box information.

The EEPROM is a page erase memory, and an entire page must

be erased before the page can be written to. Due to the page erase

requirement of the EEPROM, after writing the eighth record of

any page, the next page is automatically erased to allow for

continuous black box recording.

Each time a record is written in the black box, the device

increments the record number. Each EEPROM write records

the registers listed in Table 10.

PEC Byte

The packet error checking (PEC) byte at the end of each black

box record is specific to each record and is calculated using a

CRC-8 polynomial: C(x) = x8 + x2 + x1 + 1. The PEC byte is

calculated on the first four bytes of each record (called the

header block), one byte at a time. In a write to EEPROM, the

PEC byte is appended to the data and is the last valid byte of

that record. In a read from EEPROM, the header block of each

record is used to calculate an expected PEC code, and this

internally calculated PEC code is compared to the received PEC

byte. If the comparison fails, the PEC_ERR bit (STATUS_

CML[5]) is set, and that record is discarded because the validity

of the data has been compromised.

VOUT

PWM

FAULT

DETECTED

SHUTDOWN

DEBOUNCE

WRITE

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