BQ28550-R1 Datasheet, PDF (26/42 Pages) Texas Instruments – Single Cell Li-Ion Battery Gas Gauge

Not Recommended for New Designs
bq28550-R1
SLUSAS4A – OCTOBER 2012 – REVISED SEPTEMBER 2014
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7.6.5.7.5 Remaining Time Alert
Similar to the Remaining Capacity notification, a system may require an alarm based on time rather than
Remaining Capacity. To set a notification when remaining time to empty is less than the user-set value, the user
can set a remaining time to empty alarm alert in the system side. The remaining time to empty value determined
by the bq28550-R1 device is compared to the user-selected value. If the Remaining Time to Empty value < the
user-selected Remaining Time to Empty threshold, the host system should instruct the user of what action to
take.
7.6.5.7.6 Data Flash Interface
7.6.5.7.6.1 Accessing the Data Flash
The bq28550-R1 data flash is a non-volatile memory that contains bq28550-R1 initialization, default, cell status,
calibration, configuration, and user information. The data flash can be accessed in several different ways,
depending on what mode the bq28550-R1 device is operating in and what data is being accessed.
Commonly accessed data flash memory locations, frequently read by a system, are conveniently accessed
through specific instructions, as described in . These commands are available when the bq28550-R1 device is
either in FULL ACCESS, UNSEALED, or SEALED modes.
Most data flash locations, however, are only accessible in FULL ACCESS or UNSEALED mode by using the
bq28550-R1 evaluation software or by data flash block transfers. These locations should be optimized and/or
fixed during the development and manufacture processes. They become part of a golden image file and can then
be written to multiple battery packs. Once established, the values generally remain unchanged during end-
equipment operation.
7.6.5.7.6.2 Read-Write Access of Data Flash
To read and write commands in data flash, the following method is used:
Command Type
Write Word
Read/Write Block
SBS Command
0x00
0x2F
SBS Data
0x1yy
32-byte of data
Description
ManufacturerAccess() command to set up the data flash (DF) address
in order to write a row (32-byte) of data. Yy = the row number where
the target DF address is located.
ManufacturerInput() command. Issue this command after setting up the
DF address to read/write the 32-byte data to the DF.
The following is an example procedure to update a parameter in data flash.
1. Identify the physical byte location of the target parameter using the class and subclass ID information. This is
typically the subclass ID + Offset.
2. Identify the target row number by truncating the division of the byte location and the row length; for example,
a byte location 27 would be in row: 27 divided by 32 = row number 0.
3. Byte location within the target row is determined by: Byte Index = physical location – (row number * row
length)
Byte Index = 27 – (0 *32) = 27
The target byte is in row 0 byte 27.
4. Using MAC command 0x1yy, where yy = row number. In this example, the SMBus write command would be
0x100.
5. Read the original target row first through a block read command 0x2F before updating.
6. Store original data in memory array, so the appropriate byte(s) can be updated.
SMBus block read cmd = 0x2F, length = 32 byte
7. Store the read data into a memory array (for example, yRowDataArray).
8. Update the target byte (yRowDataArray(27).
9. Write the updated yRowDataArray() array back to the device data flash. To do this, repeat Step 4. Issue
SMBus block write cmd = 0 × 27, length 32.
10. A read verify is recommended to ensure the data flash has been re-programmed correctly. To do a read
verify, repeat Steps 4 and 5.
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