BQ27742-G1 Datasheet, PDF (25/46 Pages) Texas Instruments – Single-Cell Li-Ion Battery Fuel Gauge with Programmable Hardware Protection

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Communications (continued)
bq27742-G1
SLUSBV9C – MARCH 2014 – REVISED FEBRUARY 2016
Host Generated
GG Generated
S ADDR[6:0] 0 A
CMD[7:0] A
(a)
DATA[7:0]
A PP
S ADDR[6:0] 1 A DATA[7:0]
(b)
S ADDR[6:0] 0 A
CMD[7:0]
A Sr ADDR[6:0] 1 A
( c)
DATA[7:0]
NP
NP
S ADDR[6:0] 0 A CMD[7:0] A Sr ADDR[6:0] 1 A DATA[7:0] A . . . DATA[7:0] N P
(d)
A. 1-byte write; b. Quick read; c. 1-byte read; Incremental read (S = Start, Sr = Repeated Start, A = Acknowledge, N =
No Acknowledge, and P = Stop)
Figure 16. 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 fuel gauge 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):
S ADDR[6:0] 0 A CMD[7:0] A DATA[7:0] N PPP
Attempt to read an address above 0x7F (NACK command):
S ADDR[6:0] 0 A CMD[7:0] N PPP
Attempt at incremental writes (NACK all extra data bytes sent):
S ADDR[6:0] 0 A CMD[7:0] A DATA[7:0] A DATA[7:0] N . . . N P
Incremental read at the maximum allowed read address:
S ADDR[6:0] 0 A CMD[7:0] A Sr ADDR[6:0] 1 A DATA[7:0] A DATA[7:0] N P
Address
0x7F
Figure 17. I²C Interfaces
Data from
addr 0x74
Data from
addr 0x00
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.
7.6.2.1 I²C Time Out
The I²C engine releases both SDA and SCL lines if the I²C bus is held low for about 2 seconds. If the fuel gauge
was holding the lines, releasing them frees the master to drive the lines.
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