is this signal level ok? Please help

[runtime]

Hello All,

I want to detect the DCD signal from a modem module. The DCD Output from the module has the following voltage specs:

Output Low Voltage: 0 to 0.6 V
Output High Voltage: 2.2 to 2.75 V

I'm using a PIC18F252 at 3.3V and will wire that signal to pin RA4, this pin has the following Input voltages:

Input Low Voltage: Vss to 0.2 V
Unput High Voltage: 0.8 to Vdd

Are these signal levels ok for the PIC to detect a low and high states?

I thinl the OLV from the module (0 to 0.6) is too high, am I right? What do I need to reduce this voltage to a value between 0 and 0.2?

Thank you in advance
Peter

[Guest]

If the modem gives you an 'low' that's 0.5V, then your PIC can get confused.

Have you read the Schmitt trigger input pins' characteristics?

Does anyone else here know what to do in these situations? My guess would be to get a Schmitt trigger buffer.

[runtime]

Yes, the Schmitt trigger input pins' characteristics are:

Input Low Voltage: Vss to 0.2 V
Unput High Voltage: 0.8 to Vdd

any ideas?

[SherpaDoug]

You might also try a pull-down resistor. That would help bring the logic "0" levels down a bit.
_________________
The search for better is endless. Instead simply find very good and get the job done.

[cmdrdan]

Peter --

The 0.5 volt seems quite high for a VOL level. What is the output low current specified for the modem part at the 0.5 volt level. For a light load such as a 10k pullup resistor, I would expect that the VOL level would be lower than the 0.5 volts specified....

Dan

[PCM programmer]