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