Data Sheet

Host generated
A AS 0ADDR[6:0] CMD[7:0] Sr 1ADDR[6:0] A DATA [7:0] A DATA [7:0] PN. . .
(d) incremental read
A AS 0ADDR[6:0] CMD[7:0] Sr 1ADDR[6:0] A DATA [7:0] PN
(c) 1- byte read
A AS A0 PADDR[6:0] CMD[7:0] DATA [7:0]
(a) 1-byte write
(b) quick read
S 1ADDR[6:0] A DATA [7:0] PN
Gauge generated
. . .A AS A0 PADDR[6:0] CMD[7:0] DATA [7:0] DATA [7:0] A A
(e) incremental write
(S = Start , Sr = Repeated Start , A = Acknowledge , N = No Acknowledge , and P = Stop).
bq27441-G1
www.ti.com SLUSBH1C –NOVEMBER 2013–REVISED DECEMBER 2014
9.5.4 Communications
9.5.4.1 I
2
C Interface
The fuel gauge supports the standard I
2
C read, incremental read, quick read, one-byte write, and incremental
write functions. The 7-bit device address (ADDR) is the most significant 7 bits of the hex address and is fixed as
1010101. The first 8 bits of the I
2
C protocol are, therefore, 0xAA or 0xAB for write or read, respectively.
The quick read returns data at the address indicated by the address pointer. The address pointer, a register
internal to the I
2
C communication engine, increments whenever data is acknowledged by the fuel gauge or the
I
2
C 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).
The following command sequences are not supported:
Attempt to write a read-only address (NACK after data sent by master):
Attempt to read an address above 0x6B (NACK command):
9.5.4.2 I
2
C Time Out
The I
2
C engine releases both SDA and SCL if the I
2
C bus is held low for 2 seconds. If the fuel gauge is holding
the lines, releasing them frees them for the master to drive the lines. If an external condition is holding either of
the lines low, the I
2
C engine enters the low-power SLEEP mode.
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