Datasheet

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SLUS491 – JULY 2001
10
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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
LSB
MSB
11 00 0
73h = 01110011
MSB
LSB
Received by Host from bq26231
10100110
65h = 0 1 1 0 0 1 0 1
MSB LSB
0 1 2 3 4 5 6 7
CMDR = 73h
LSB
MSB
0 1 2 3 4 5 6 7
Data (OFR) = 65h
1 1 1
Figure 4. Typical Communication With the bq26231
Send Host to bq-HDQ
CMDR
Break
Start-Bit Address-Bit/Data-Bit Stop-Bit
LSB
Bit0
R
/W
MSB
Bit7
Send Host to bq-HDQ or
Receive From bq-HDQ
Data
t
(RSPS)
Address
Figure 5. Communication Frame Example