BQ2060A_15 Datasheet, PDF (19/61 Pages) Texas Instruments – SBS v1.1-Compliant Gas Gauge IC

bq2060A
www.ti.com
SLUS500D – OCTOBER 2001 – REVISED OCTOBER 2011
SMBus
The SMBus interface is a command-based protocol. A processor acting as the bus master initiates
communication to the bq2060A by generating a START condition. A START condition consists of a high-to-low
transition of the SMBD line while the SMBC is high. The processor then sends the bq2060A device address of
0001011 (bits 7–1) plus a R/W bit (bit 0) followed by an SMBus command code. The R/W bit and the command
code instruct the bq2060A to either store the forthcoming data to a register specified by the SMBus command
code or output the data from the specified register. The processor completes the access with a STOP condition.
A STOP condition consists of a low-to-high transition of the SMBD line while the SMBC is high. With SMBus, the
most significant bit of a data byte is transmitted first.
In some instances, the bq2060A acts as the bus master. This occurs when the bq2060A broadcasts charging
requirements and alarm conditions to device addresses 0x12 (SBS Smart Charger) and 0x10 (SBS Host
Controller.)
SMBus Protocol
The bq2060A supports the following SMBus protocols:
• Read Word
• Write Word
• Read Block
A processor acting as the bus master uses the three protocols to communicate with the bq2060A. The bq2060A
acting as the bus master uses the Write Word protocol.
The SMBD and SMBC pins are open drain and require external pullup resistors.
SMBus Packet Error Checking
The bq2060A supports Packet Error Checking as a mechanism to confirm proper communication between it and
another SMBus device. Packet Error Checking requires that both the transmitter and receiver calculate a Packet
Error Code (PEC) for each communication message. The device that supplies the last byte in the communication
message appends the PEC to the message. The receiver compares the transmitted PEC to its PEC result to
determine if there is a communication error.
PEC Protocol
The bq2060A can receive or transmit data with or without PEC. Figure 9 shows the communication protocol for
the Read Word, Write Word, and Read Block messages without PEC. Figure 8 includes PEC.
In the Write Word protocol, the bq2060A receives the PEC after the last byte of data from the host. If the host
does not support PEC, the last byte of data is followed by a STOP condition. After receipt of the PEC, the
bq2060A compares the value to its calculation. If the PEC is correct, the bq2060A responds with an
ACKNOWLEDGE. If it is not correct, the bq2060A responds with a NOT ACKNOWLEDGE and sets an error
code.
In the Read Word and Block Read, the host generates an ACKNOWLEDGE after the last byte of data sent by
the bq2060A. The bq2060A then sends the PEC and the host acting as a master receiver generates a NOT
ACKNOWLEDGE and a STOP condition.
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