DESIGN OF A CUSTOM ASIC INCORPORATING CAN™ AND 1 ...

attachments, microcontroller with built-in 1 – Wire® Master, synthesizable 1 – Wire® Bus
Master, and serial interface protocol conversions [8].
Since data on any 1 – Wire® network is transferred by time slots, a system clock is not
required, as each 1 – Wire® device is self-clocked by its own internal oscillator synchronized to
the falling edge of the master. The first part of communication on any 1 – Wire® network
involves the selection of a 1 – Wire® slave device for communications. This can be
accomplished by selecting all slave devices (i.e. broadcast), selecting a specific slave device
(using the serial number of the device), or discovering the next slave on the bus using a binary
search algorithm. Not to be confusing, all slave devices can be selected, but the 1 – Wire®
Master can only communicate with one slave at a time. Once a slave has been selected, all other
slaves drop out and ignore subsequent communications until the next reset is issued. At this
point, the bus master can issue device-specific commands to the selected slave, send data to it, or
read data from it.
In a typical 1 – Wire® network there will be more than one slave and also different types
of slave devices. Because each slave type (see section 2.4) performs different functions and
serves a different purpose, each has a unique communication sequence once it has been selected
[11]. Even though each slave type may have a different communication sequence and features,
they all have the same selection process and follow the command flow shown in Figure 2.2.
Figure 2.2 Typical 1 – Wire® Communication Flow [11].
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