BQ29312A Datasheet, PDF (16/35 Pages) Texas Instruments – TWO-CELL, THREE-CELL, AND FOUR-CELL LITHIUM-ION OR LITHIUM-POLYMER BATTERY PROTECTION AFE

bq29312A
SLUS629A – JANUARY 2005 – REVISED AUGUST 2005
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Communications
The I²C compatible serial communications provides read and write access to the bq29312A data area. The data
is clocked via separate data (SDATA) and clock (SCLK) pins. The bq29312A acts as a slave device and does
not generate clock pulses. Communication to the bq29312A is provided from GPIO pins or an I²C supporting port
of a host system controller. The slave address for the bq29312A is 7 bits and the value is 0100 000 (0x20).
(MSB)
(MSB)
Write ⁽¹⁾
0
1
Read
I²C ADDRESS +R/W BIT
I²C ADDRESS (0x20)
0
0
0
0
(LSB)
0
(LSB)
0
1
(1) Bit 0: 0 = write, 1= read
The bq29312A does not have the following functions compatible with the I²C specification.
• The bq29312A is always regarded as a slave.
• The bq29312A does not return a NACK for an invalid register address.
• The bq29312A does not support the general code of the I²C specification, and therefore does not return an
ACK.
• The bq29312A does not support the address auto increment, which allows continuous reading and writing.
• The bq29312A allows data to be written to or read from the same location without resending the location
address.
SCLK
…
…
…
SDATA
Start
A6 A5 A4 ^… A0 R/W ACK
0
0
Slave Address
R7 R6 R5 ^… R0 ACK
0
Register Address
D7 D6 D5 ^… D0 ACK
Data
0
Stop
Note: Slave = bq29312
Figure 4. I²C-Bus Write to bq29312A
SCLK
…
…
…
…
SDATA A6 A5 ^… A0 R/W ACK
Start
00
Slave Address
Note: Slave = bq29312
R7 R6 ^… R0 ACK
0
Register Address
A6
A0 R/W ACK
10
Slave Address
D7 D6 ^… D0 NACK
Slave Drives
The Data
Data
Stop
Master Drives
NACK and Stop
Figure 5. I²C-Bus Read from bq29312A: Protocol A
SCLK
…
…
…
…
SDATA _{A6 A5} … _{A0 R/W ACK}
Start
00
Slave Address
Note: Slave = bq29312
R7 R6 ^… R0 ACK
A6 A5 ^… A0 R/W ACK D7 ^… D0 NACK
Register
Address
0
Stop Start
Slave Address
Slave Drives
The Data
Stop
Master Drives
NACK and Stop
Figure 6. I²C-Bus Read from bq29312A: Protocol B
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