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Altera_Forum's avatar
Altera_Forum
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17 years ago

A very basic newbie question

Hi All I have a very basic question. I've recently started learning about CPLD and VHDL. My VHDL code usually compiles and simulates fine, but when I put it in an actual CPLD it behaves really...
Altera_Forum's avatar
Altera_Forum
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17 years ago

Just a couple of clues for you.

1) when usinglow frequencies try to drive your led with the clock signal (pull it out from the CPLD) and see if it goes ON/OFF regularly, it is a very simple "oscilloscope". You may try to measure the DC voltage with a digital multimeter on both the divided clock (you should measure Vcc/2 with higher frequencies or discriminate the two logic levels with very low frequencies) and the original clock generated by the microcontroller.

2) use a 22ohm resistor in series with the clock input signal to the CPLD, it may reduce or cancel some unwanted signal bouncings.

Without an oscilloscope is a bit hard, but you can do it!

Good luck.