Honored ContributorI have used the CPLD for my project.
And the device is EPM7128STC100-10(Max7000 series ) ,the voltage of Vccio is 5v,but the output voltage of the I/O is 3.16v. I have defined the I/O standard as TTL.And the unused pins are set as input tri_stated. I want to know that what's the problem.Is that normal. That's all.Thank you!
Honored Contributorwhat is connected on that io pin of your cpld ?
is every io pin only reaching 3.16 v or is this the only one ?Honored ContributorIt's a valid TTL high level (>2.4V), and according to the MAX7000 datasheet, it's normal operation. The specification is Voh > 2.4V @ Ioh = -4mA, although the typical current capability is higher according to the diagram. But if you havn't any intentional load connected to the pin, you may want to check what's going on in your circuit.
Honored ContributorNo device is connected to the cpld.and the voltage of all pins are 3.16v.
--- Quote Start --- what is connected on that io pin of your cpld ? is every io pin only reaching 3.16 v or is this the only one ? --- Quote End ---Honored ContributorAlthough not strictly contradicting the device manual, it seems strange, Are you sure to have connected all VCCIO pins to +5V and that the device is actually configured, when you perform the measurement? Is the design operating as expected in general?
Honored ContributorI have checked the VCCIO serval times.There is no problem,that is,Vccio=5v.
And I am sure that the device is configured. I think that the cpld is destroyed ,but the cpld can control the devices behind with the output voltage of 3.16v. --- Quote Start --- Although not strictly contradicting the device manual, it seems strange, Are you sure to have connected all VCCIO pins to +5V and that the device is actually configured, when you perform the measurement? Is the design operating as expected in general? --- Quote End ---Honored ContributorCan you tell me that whether Voh>2.4v is under the condition that there isn't any intentional load connected to the pin.
Thank you! ps:I have try my best,but it doesn't work .can you check the schematic diagram for me. --- Quote Start --- It's a valid TTL high level (>2.4V), and according to the MAX7000 datasheet, it's normal operation. The specification is Voh > 2.4V @ Ioh = -4mA, although the typical current capability is higher according to the diagram. But if you havn't any intentional load connected to the pin, you may want to check what's going on in your circuit. --- Quote End ---
