DS1808
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READING THE DS1808
As shown in Figure 4, the DS1808 provides one read command operation. This operation allows the user
to read both potentiometers. To initiate a read operation, the R/W bit of the command/control byte is set
to 1. Communication to read the DS1808 begins with a start condition, which is issued by the master
device. The command/control byte from the master device will follow the start condition. Once the
command/control byte has been received by the DS1808, the part will respond with an acknowledge.
When the master has received the acknowledge from the DS1808, the master can then begin to receive
wiper data. The value of the wiper of potentiometer-0 will be the first returned from the DS1808. It will
then be followed by the value of potentiometer-1. Once the 8-bits of potentiometer-0 have been
transmitted, the master will need to issue an acknowledge, unless it is the only byte to be read, in which
case the master issues a ‘not acknowledge.’ If desired, the master may stop the communication transfer at
this point by issuing the stop condition. However, if the value of the remaining potentiometer is needed,
transfer can continue by clocking the 8 bits of the potentiometer-1 value, followed by a not acknowledge.
WRITING TO THE DS1808
A data flow diagram of the DS1808 is shown in Figure 5. The DS1808 has one write command that is
used to change the position of the wiper(s). All write operations begin with a START from the master,
followed by a command/control byte. The R/W bit should be written to 0b, which initiates a write
command. Once the command/control byte has been issued and the master receives the
ACKNOWLEDGE from the DS1808, potentiometer wiper data is transmitted to the DS1808 by the
master device.
Figure 2
