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Input High Voltage....

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S.K

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Hi all,

What is the meaning of Input High Voltage, Input Low Voltage, Output High Voltage, Output Low Voltage as attached? Lets say I'm using 3V as Vdd.

Also, how do you guys program a graphic LCD to display a waveform from a function generator?


S.K
 

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S.K said:
What is the meaning of Input High Voltage, Input Low Voltage, Output High Voltage, Output Low Voltage as attached? Lets say I'm using 3V as Vdd.
Output High/Low voltage is the voltage one measured on a PIC output pin when a certain load is connected or the PIC is sinking certain load current.

In the attached specification image, VoH @10mA loading is specified as Vdd-0.8=3-0.8=2.2V. You would expect a voltmeter to read 2.2V at the PIC pin with a 10mA loading(e.g. a 30:eek:hm: resistor is connected to 0V). Similarly, VoL @25mA is the PIC pin voltage when it is sinking 25mA of current.

ViH and ViL is the input voltage that the PIC would consider it the proper level for logic HIGH or LOW. So, you must provide the PIC logic input pin with a voltage of 3Vx0.7=2.1V or higher if you want the PIC to see the voltage as logic HIGH. Same applies to VoL, which is 3Vx0.3=0.9V. Any voltage below 0.9V is seen by the PIC as logic LOW.

If the input logic voltage is in the range 0.9V~2.1V, it is out of spec and anything can happen and the logic level seen by the PIC might not be correct.
 
S.K said:
Hi all,

Also, how do you guys program a graphic LCD to display a waveform from a function generator?

S.K

This can be a little tricky if you are not sure of the concept. In it's basic form you convert the time/voltage to an x/y value which you then plot on the graphic LCD screen. This becomes tricky because most screens do not have a straight forward x/y display setup, it's more lines and character positions. You have to select the correct line and then translate the pixel data into a 'character'. It is quite an advanced project.
 
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