BQ27500 Datasheet, PDF (33/39 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge

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7 COMMUNICATIONS
bq27500
bq27501
System-Side Impedance Track™ Fuel Gauge
SLUS785 – SEPTEMBER 2007
7.1 I²C INTERFACE
The fuel gauge supports the standard I²C read, incremental read, one-byte write quick read, and
functions. The 7-bit device address (ADDR) is the most significant 7 bits of the hex address and is fixed as
1010101. The 8-bit device address is therefore 0xAA or 0xAB for write or read, respectively.
Host generated
Fuel Gauge Generated
(a) 1-byte write
(b) quick read
(c) 1-byte read
(d) incremental read
(S = Start, Sr = Repeated Start, A = Acknowledge, N = No Acknowledge, and P = Stop).
Figure 7-1. Supported I²C Formats
The quick read returns data at the address indicated by the address pointer. The address pointer, a
register internal to the I²C communication engine, increments whenever data is acknowledged by the
bq27500 or the I²C master. Quick writes function in the same manner and are a convenient means of
sending multiple bytes to consecutive command locations (such as two-byte commands that require two
bytes of data).
Attempt to write a read-only address (NACK after data sent by master):
Attempt to read an address above 0x7F (NACK command):
Attempt at incremental writes (NACK all extra data bytes sent):
Incremental read at the maximum allowed read address:
The I²C engine releases both SDA and SCL if the I²C bus is held low for t_(BUSERR). If the fuel gauge was
holding the lines, releasing them frees the master to drive the lines. If an external condition is holding
either of the lines low, the I²C engine enters the low-power sleep mode.
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