Electronic Design

1Wire Networking

1Wire is Maxim Integrated Products' proprietary network architecture. Benefits derived from this low-cost master/slave architecture include the ability to provide small amounts of power on the same line used for communication.

A 1Wire master can be easily implemented on an MCU via software using only a single I/O pin. Many MCUs already have 1Wire master routines. Bridge chips for USB-to-1Wire and serial-to-1Wire are available.

There's no licensing restriction on the master. On the other hand, licensing comes into play with slaves, because each slave has a unique 64-bit serial number. The initial handshaking protocol allows the master to uniquely identify each slave.

Hal Kurkowski, managing director of Automatic Information Products at Dallas Semiconductor/Maxim, points out that the 1Wire approach can supply power to slave devices (see the figure). A capacitor maintains the voltage at the device while data is transferred.

It's possible to configure the master to provide more power via the bus when necessary. In this case, the master must be programmed so the alternate 22-Ω supply resistor is switched in after a request is sent to the slave device. An example would be a flash-based memory device that requires more power to program the memory. The master would send the request to the device, switch in the alternate power supply, wait for a prescribed amount of time, and then switch back the 1.2-kΩ resistor.

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