| 摘要 |
<p>PURPOSE:To avoid a trouble by manual operation by allowing each package to detects whether or not it is located at a remotest position and validating a pull-up resistor when the package is located at the remotest position. CONSTITUTION:When a voltage at a tap tz of a voltage divider is larger than a reference voltage VR, a comparator COMP causes an output, a relay Ry closes its contact to connect the resistor R to a power supply +V. Thus, the signal line l and the bus B are subjected to pull-up. The higher voltage of the tap tz takes place only when the said package is located at the remotest position. Then each package itself detects whether it is mounted to the terminating point or not, the pull-up resistor is validated when the package is mounted at the termination point, and the pull-up resistor is invalidated when the package is not mounted at the termination point and only one pull-up resistor is realized automatically at the remotest point.</p> |
