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

serves as a device address on the bus. The 8-bit family code, a subset of the 64-bit ID, identifies
the device type and functionality.
What makes the 1 – Wire® protocol unique is that it is the only voltage-based digital
system that works with two contacts, data and ground, for half-duplex bidirectional
communication. In contrast to other serial communication systems such as I 2 C [9] or SPI, 1 –
Wire® devices are designed for use in a contact environment. Either disconnecting from the 1 –
Wire® bus or a loss of contact puts the 1 – Wire® slaves into a defined reset state. When the
voltage returns, the slaves wake up and signal their presence. With only one contact to protect,
the built-in ESD protection of 1 – Wire® devices is extremely high. With two contacts, 1 –
Wire® devices are the most economical way to add electronic functionality to nonelectronic
objects for identification, read/write memories, authentication, addressable switches, digital
temperature sensors, and delivery of calibration data or manufacturing information [10].
2.3 1 – Wire® Communication
To take advantage of 1 – Wire® technology, a 1 – Wire® Master that can generate the
waveforms to identify the devices on the bus and to communicate with them is required. There
are numerous ways to construct a 1 – Wire® Master. The differences depend on whether the 1 –
Wire® Master is for a short network (e.g. those that do not extend beyond a radius of 1 meter
and have no more than three to five slaves) or for a larger network (e.g. those that can extend the
radius beyond 1 meter to over 500 meters and can have hundreds of slaves). In general, 1 –
Wire® Master implementations can be grouped into four categories: microprocessor port-pin
9