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“接口”是指从单片机1/O口,到被控制对象的连接方法的综合称呼。这种连接方法绝不是简单地用导线连起来,其中还包括电流、电压的匹配问题。 以AT89C2051单片机为例,其1/O口的最高耐压是6.5V;输出高电平时,外拉电流为80μA时,电位不低于2.4V;输出低电平时,灌入电流为20mA时,电平不高于0.45V。由于单片机为高、低电平时1/O的外拉和灌入电流相比差着近千倍,因此设计者多用低电平启动设备运转,高电平今设备停止。AT89C2051复位后的1/O口都是高电平,此时受控设备应是静止的。 在用单片机进行实际控制时,往往不能完全满足这些条件,若超出这些条件,单片机的稳定性将不能保证。 发光二极管点亮的电压、电流都很低,电压2V、电流3～10mA都能点亮。这样的电压、电流都在AT89C2051单片机允许的范围内。因此可以将AT89C2051的1/O口串联在发光二
“Interface” refers to the microcontroller from the 1 / O port, to the controlled object of the connection method of the general term. This connection method by no means simply wire together, which also includes the current and voltage matching problems. AT89C2051 microcontroller, for example, the maximum voltage of 1 / O port is 6.5V; output high, the pull-out current of 80μA, the potential of not less than 2.4V; output low, the sinking current of 20mA, The level is not higher than 0.45V. As the microcontroller is high, 1 / O low pull-out and sink current compared to nearly a thousand times worse, so designers use more low-level start device operation, high-level device stops. AT89C2051 1 / O port after reset are high, the controlled equipment should be static at this time. In the actual control with the microcontroller, often can not fully meet these conditions, if beyond these conditions, the stability of the microcontroller will not be guaranteed. Light-emitting diode lighting voltage and current are very low, voltage 2V, current 3 ~ 10mA can light. This voltage and current are within the allowable range of AT89C2051 microcontroller. Therefore, the AT89C2051 1 / O port in series two light