Input pin voltage levels

[Andres Rodriguez]

I am trying to find out the minimum and maximum voltage levels that will cause an input pin to be high or low.
I am using a 28X to make a tachometer with a Fairchild QRB1134. With the "count" instruction determine the number of times that there is a high/low change in 1 second.

 

[lahaye]

Hello Marmitas,

In this Thread by hippy you will find the specifications regarding voltage-thresholds for Input pins: http://www.picaxeforum.co.uk/showthread.php?t=8609. If this link doesn't work search for the title "PICAXE Input Pin Types".

Regards
Florian

 

[westaust55]

The typical datasheet for a PIC chip will indicate teh following ABSOLUTE MAXIMUM value:

Voltage on all other pins with respect to VSS ......................................................... -0.3V to (VDD + 0.3V)

In other words, all input pins MUST be kept between Vss (0 volts) and Vdd + 0.3V (or say 4.5+0.3 = 4.8V and 5+ 0.3 = 5.3V) at ALL times.

In reality you should never exceed Vdd which is the voltage you are using to power the PICAXE chip.

 

[Andres Rodriguez]

Thank you gentlemen, the project is working.
Andres