DS2786B Maxim Integrated Products, DS2786B Datasheet - Page 19

• Manufacturer Part Number: DS2786B
• Description: Stand-Alone OCV-Based Fuel Gauge
• Manufacturer: Maxim Integrated Products

A bus master initiates communication with a slave
device by issuing a START condition followed by a
slave address (SAddr) and the read/write (R/W) bit.
When the bus is idle, the DS2786B continuously moni-
tors for a START condition followed by its slave
address. When the IC receives an address that match-
es its slave address, it responds with an Acknowledge
bit during the clock period following the R/W bit. The
DS2786BG-C3 7-bit slave address is 0110110. The
upper 3 bits are fixed at 011; the lower 4 bits can be
changed by writing the I
Register at location 7Dh.
The R/W bit following the slave address determines the
data direction of subsequent bytes in the transfer. R/W
= 0 selects a write transaction, with the following bytes
being written by the master to the slave. R/W = 1 selects
a read transaction, with the following bytes being read
from the slave by the master. With the ADDR3–ADDR0
bits at their default of 0110, writes occur using address
0x6Ch, while reads occur at 0x6Dh.
Figure 24. I
Figure 25. DS2786B I
Table 5. 2-Wire Protocol Key
X—RESERVED.
ADDR3:0—USER-ADJUSTABLE BITS OF THE DS2786BG-C3’S I
MAddr
SAddr
FCmd
KEY
Data
A
N
ADDR3
S
BIT 7
BIT 7
0
2
C Address Configuration Register Format
START bit
Slave address (7 bit)
Function command byte
Memory address byte
Data byte written by master
Acknowledge bit—master
No acknowledge—master
______________________________________________________________________________________
2
ADDR2
C Address Byte Format
BIT 6
BIT 6
1
DESCRIPTION
2
C Address Configuration
Stand-Alone OCV-Based Fuel Gauge
ADDR1
BIT 5
BIT 5
1
Read/Write Bit
Slave Address
ADDR0
ADDR3
BIT 4
BIT 4
ADDRESS 7Dh
2
C ADDRESS. FACTORY DEFAULT IS 0110.
The DS2786B is compatible with any bus timing up to
400kHz. No special configuration is required to operate
at any speed.
The command protocols involve several transaction for-
mats. The simplest format consists of the master writing
the START bit, slave address, and R/W bit, and then
monitoring the Acknowledge bit for presence of the
DS2786B. More complex formats such as the write
data, read data, and function command protocols write
data, read data, and execute device-specific opera-
tions. All bytes in each command format require the
slave or host to return an Acknowledge bit before con-
tinuing with the next byte. Each function command defi-
nition outlines the required transaction format. Table 5
applies to the transaction formats.
ADDR2
BIT 3
BIT 3
KEY
Data
X
Sr
W
R
A
N
P
Repeated START
R/W bit = 0
R/W bit = 1
STOP bit
Data byte returned by slave
Acknowledge bit—slave
No acknowledge—slave
ADDR1
BIT 2
BIT 2
X
2-Wire Command Protocols
DESCRIPTION
ADDR0
BIT 1
BIT 1
X
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Bus Timing
BIT 0
BIT 0
R/W
X
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