bq20z80-V101
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SLUS625D–SEPTEMBER 2004–REVISED OCTOBER 2005
Gas Gauge
Figure 2. SMBus Communication Protocol With PEC
PEC Calculation
PEC calculation is an 8-bit cyclic redundancy check (CRC-8) based on the polynomial C(X) = X8 + X2 + X1 + 1
All bytes in the transmission are used in the calculation, including: Address, Command, and Data.
Not included: ACKNOWLEDGE, NOT ACKNOWLEDGE, start, stop, and repeated start.
STANDARD SBS COMMANDS
The bq20z80 SBS commands meet the SBD v1.1 specification.
ManufacturerAccess( ) (0x00)
This read- or write-word function provides battery-system level data, access to test controls, and security
features.
System Data (Returns Data)
The commands in this section provide data to be read from 0x00 after the command has been written.
Device Type: 0x0001, Returns IC part number. 0x0800 - The number is not stored in data flash, but is part of
the instruction flash.
Firmware Version: 0x0002, Returns the firmware version. This is not stored in data flash, but is part of the
instruction flash. Its format is most-significant byte (MSB)
= Decimal integer, and the
least-significant byte (LSB) = sub-decimal integer, e.g., 0x0120 = version 01.20.
Hardware Version: 0x0003, Returns the hardware version stored in single byte of reserved data flash. E.G.:
0xa2 = Version A2.
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