| 摘要 |
PURPOSE:To minimize the power loss of a control element and to attain the direct control even with a heavy load by programming the port of the control element into an application for input when the control element is controlled at a high level. CONSTITUTION:When a transistor TR4 is controlled at a high level, an output buffer 2a is set at a high impedance by an input/output switching signal and a port is programmed into an application for input. As a result, no current flows from the buffer 2a. Furthermore no current flows to an input buffer 2b since this buffer is also set at a high impedance. Therefore no current flows virtually from an element 1. Thus the current flowing to the TR4 is decided only by a resistance 7 connected to a power supply. While the port of the element 1 is programmed into an application for output in case the TR4 is controlled at a low level.
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