Datasheet

21Maxim Integrated
DS2484
Single-Channel 1-Wire Master
with Adjustable Timing and Sleep Mode
Table 10. I
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C Communication—Legend
Table 11. Data Direction Codes
Not Acknowledged by Slave: A slave device could
be unable to receive or transmit data, e.g., because
it is busy performing a real-time function or is in
sleep mode. In this case, the slave device does not
acknowledge its slave address and leaves the SDA
line high. A slave device that is ready to communicate
acknowledges at least its slave address. However,
some time later the slave can refuse to accept data,
e.g., because of an invalid command or parameter.
In this case, the slave device does not acknowledge
any of the bytes that it refuses and leaves SDA high.
In either case, after a slave has failed to acknowledge,
the master first should generate a repeated START
condition or a STOP condition followed by a START
condition to begin a new data transfer.
Not Acknowledged by Master: At some time when
receiving data, the master must signal an end of data
to the slave device. To achieve this, the master does
not acknowledge the last byte that it has received
from the slave. In response, the slave releases SDA,
allowing the master to generate the STOP condition.
Writing to the DS2484
To write to the DS2484, the master must access the
device in write mode, i.e., the slave address must be sent
with the direction bit set to 0. The next byte to be sent is
a command code, which, depending on the command,
may be followed by a command parameter. The DS2484
acknowledges valid command codes and expected/
valid command parameters. Additional bytes or invalid
command parameters are never acknowledged.
Reading from the DS2484
To read from the DS2484, the master must access the
device in read mode, i.e., the slave address must be sent
with the direction bit set to 1. The read pointer determines
the register that the master reads from. The master can
continue reading the same register over and over again,
without having to readdress the device, e.g., to watch
the 1WB changing from 1 to 0. To read from a different
register, the master must issue the Set Read Pointer com-
mand and then access the DS2484 again in read mode.
I
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C Communication Examples
See Table 10 and Table 11 for the I
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C communication
legend and data direction codes.
SYMBOL DESCRIPTION
S START Condition
AD, 0 Select DS2484 for Write Access
AD, 1 Select DS2484 for Read Access
Sr Repeated START Condition
P STOP Condition
A Acknowledged
A\ Not Acknowledged
(Idle) Bus Not Busy
<byte> Transfer of One Byte
DRST Command “Device Reset” (F0h)
SRP Command “Set Read Pointer” (E1h)
WCFG Command “Write Device Configuration” (D2h)
ADJP Command “Adjust 1-Wire Port” C3h)
1WRS Command “1-Wire Reset” (B4h)
1WSB Command “1-Wire Single Bit” (87h)
1WWB Command “1-Wire Write Byte” (A5h)
1WRB Command “1-Wire Read Byte” (96h)
1WT Command “1-Wire Triplet” (78h)
Master-to-Slave Slave-to-Master