Rainbow Electronics DS2482-800 - Manual (Page 17)

DS2482-800: Eight-Channel 1-Wire Master
17 of 22
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.
Figure 10. I²C Timing Diagram
SCL
SDA
STOP START
t
BUF
t
HD:STA
t
LOW
t
R
t
HD:DAT
t
HIGH
t
SU:DAT
Repeated
START
t
SU:STA
t
F
t
HD:STA
t
SP
t
SU:STO
Spike
Suppression
NOTE: Timing is referenced to V
ILMAX
and V
IHMIN
.
Writing to the DS2482
To write to the DS2482, 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 DS2482 will acknowledge valid command codes and expected/valid
command parameters. Additional bytes or invalid command parameters will never be acknowledged.
Reading from the DS2482
To read from the DS2482, 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 will read from. The master
may continue reading the same register over and over again, without having to re-address 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
command and then access the DS2482 again in read mode.
I²C Communication—Legend
SYMBOL DESCRIPTION SYMBOL DESCRIPTION
S START Condition DRST Command "Device Reset", F0h
AD,0 Select DS2482 for Write Access WCFG Command "Write Configuration", D2h
AD,1 Select DS2482 for Read Access CHSL Command "Channel Select", C3h
Sr Repeated START Condition SRP Command "Set Read Pointer", E1h
P STOP Condition 1WRS Command "1-Wire Reset", B4h
A Acknowledged 1WWB Command "1-Wire Write Byte", A5h
A\ Not Acknowledged 1WRB Command "1-Wire Read Byte", 96h
(Idle) Bus Not Busy 1WSB Command "1-Wire Single Bit", 87h
Transfer of 1 Byte 1WT Command "1-Wire Triplet", 78h