| 摘要 |
Apparatus and method are provided for saving and (upon demand) restoring a control signal for a signal-controlled system. A control signal generated by or within that system is provided to a multiplexer, which normally produces that control signal. That control signal is digitized and stored by a storage device as follows. The output of the storage device is provided both to the multiplexer and to a comparator. The comparator also receives the output of the multiplexer, and compares the output of the storage device and the multiplexer. The comparator provides a signal to the storage device to increment or decrement the storage device based on whether the signal produced by the storage device is less than, or greater than or equal to, the control signal produced by the multiplexer. The multiplexer output is also provided to the signal-controlled system to provide the control signal thereto. Upon demand as indicated by a selection signal provided to the multiplexer, the stored signal from the storage device is outputted by the multiplexer, and is accordingly provided by the multiplexer to the system as the control signal. The storage device includes a resistor ladder having a plurality of evenly or unevenly incremented outputs, a selector for selecting one of those outputs to be provided to the multiplexer and to the comparator, and a counter controlled by the comparator for controlling operation of the selector.
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