BQ26231 Datasheet, PDF (10/18 Pages) Texas Instruments – LOW COST BATTERY COULOMB COUNTER FOR EMBEDDED PORTABLE APPLICATIONS

bq26231
SLUS491 – JULY 2001
APPLICATION INFORMATION
communicating with the bq26231 (continued)
The return-to-one data bit frame consists of three distinct sections. The first section is used to start the
transmission by either the host or the bq26231 taking the HDQ pin to a logic-low state for a period t_(STRH,B). The
next section is the actual data transmission, where the data should be valid by a period t_(DSU,B) after the negative
edge used to start communication. The data should be held for a period t_(DV) / t_(DH), to allow the host or bq26231
to sample the data bit.
The final section is used to stop the transmission by returning the HDQ pin to a logic-high state by at least a
period t_(SSU,B) after the negative edge used to start communication. The final logic-high state should be held
for a period t_(CYCH,B), to allow the bit transmission to cease properly. The Standard Serial Communication
Timing Specification table and Figure 1 give the timings for data and break communication.
Communication with the bq26231 always occurs with the least-significant bit being transmitted first. Figure 4
shows an example of a communication sequence to read the bq26231 OFR register.
Break
Written by Host to bq26231
CMDR = 73h
LSB
MSB
0
1
2
3
4
5
6
7
Received by Host from bq26231
Data (OFR) = 65h
LSB
MSB
0 12 345 67
11
0
01
1
1
0
1
01
0 01 1
0
MSB LSB
73h = 01110011
MSB LSB
65h = 0 1 1 0 0 1 0 1
Figure 4. Typical Communication With the bq26231
Send Host to bq-HDQ
CMDR
Send Host to bq-HDQ or
Receive From bq-HDQ
Data
Break
LSB
Bit0
Address
Start-Bit
Address-Bit/Data-Bit Stop-Bit
R/W
MSB
Bit7
t(RSPS)
Figure 5. Communication Frame Example
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