| 摘要 |
Multiple level logic bus drivers and receivers communicate over a bus using a multiple-level logic protocol that transfers multiple bits on each signal wire of a bus in a given interval without increasing the bus width or power dissipation. In one embodiment, four logic levels are employed using CMOS transistor circuitry operating with low voltage (e.g., 1.2V or 1.3V) power supplies (Vdd) and P and N transistor threshold voltage levels of Vtp and Vtn on the order of 0.4--0.5V. Thus, the separation between the following four logic levels is approximately uniform: Vdd; Vdd-Vtp; Vss+Vtn; and Vss. The approximately equal voltage gaps between each quantization level provide uniform noise margins for all levels. A bus noise minimization scheme and a quick recovery scheme ensure the correct data transfer in the presence of injected noise. An initial over drive feature is disclosed for shorter transition times.
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