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

All 1 – Wire® masters described in sections 2.3.2 through 2.3.4 support overdrive speed.
In section 2.3.1, the overdrive speed support depends on the capabilities of the
microcontroller (i.e. clock rate and number of clock cycles per instruction cycle).
Active PullupThe 1 – Wire® bus or network is an open-drain environment, with 0V
(logic 0) being the active state. When the bus is idle, it is pulled high to the pullup
voltage through a resistor (RPUP). Falling edges, consequently, are sharp; rising edges,
due to the resistor and the parasitic supply, can be quite slow. Active pullup refers to a
method that tests rising edges, and, if a specific threshold has been crossed, bypasses the
pullup resistor for a limited time with a low-impedance path. Active pullup is generally
not needed in short networks or with a single slave device. If available, active pullup
recharges the 1 – Wire® line faster than resistive pullup and, therefore, supports multiple
1 – Wire® slaves in the network without having to extend the recovery time between
time slots. The 1 – Wire® masters covered in section 2.3.4 differ in the strength
(impedance) of the bypass and the method that controls the duration of the active pullup
[8].
A typical 1 – Wire® net-based system consists of three main elements: a bus master with
controlling software or 1 – Wire® interface, the electrical connection between master and slaves,
and the 1 – Wire® devices, i.e. slaves. The primary job of the 1 – Wire® Master is to initiate
and control the communication with one or more 1 – Wire® slave devices on the bus. Each
slave device has a unique, unalterable, factory-programmed 64-bit identification number, which
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