Parasite Powering Issues
The 1-Wire waveform must not only be sufficient for communication, but also provide operating power for the slaves. Each slave "robs" power from the bus when the voltage on the bus is greater than the voltage on its internal energy storage capacitor. When the weight of the network becomes excessive, the current delivered by the master may not be sufficient to maintain operating voltage in the slaves.
The worst-case scenario for parasite power is a very long sequence of zero bits issued by the master. When this occurs, the line spends most of its time in the low state, and there is very little opportunity to recharge the slaves. If the bus reaches a sufficient voltage during the recovery time between bits and if the recovery time is long enough, there is no problem. As the internal operating voltage in each slave drops, the slave's ability to drive the bus to make zero bits is reduced, and the timing of the slave changes. Eventually, when the parasite voltage drops below a critical level, the slave enters a reset state and stops responding. Then, when the slave again receives sufficient operating voltage, it will issue a presence pulse and may corrupt other bus activity in doing so. When a network has insufficient energy to maintain operating power in the slaves, failures will be data-dependent and intermittent.