UART attachments
There are two ways to create 1-Wire communication through a UART. The traditional way uses the timing capabilities of the UART
directly, but has to invest one character to generate one time slot or the reset-/presence-detect sequence. This concept is
described in application note 214, "Using a UART to Implement a 1-Wire Bus Master." Although efficient under operating systems
such as DOS, modern operating systems make the access to UART registers quite inefficient. For this reason, this type of UART
attachment is no longer popular for 1-Wire applications.
The new UART attachment uses a special protocol converter chip, the DS2480B, to generate 1-Wire communication. This device
increases the efficiency (one character for 8 time slots) and allows 1-Wire overdrive speed. This type of interface is discussed in
category 4, Serial Interface Protocol Conversions, of application note 4206 (see above). If properly configured (see application note
4104, "Understanding and Configuring the 1-Wire Timing of the DS2480B"), the DS2480B can drive more than 30 slaves in
standard speed and at least nine in overdrive speed. The DS2480B is the only integrated 1-Wire master that can program EPROM
devices.