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Altera_Forum
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16 years ago

MAX3000 CPLD bi-directional I/O with 5V pull-up

Hi How would I create a bi-directional pin with open-collector output on a MAX3000 CPLD? I have started the design with an open collector driver driving the pin and a 541 type buffer fo...
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Altera_Forum
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16 years ago

Hi

My application is working. I must be honest and say that I am not 100% sure that I have done everything correctly as this is the first time that I am using a modern CPLD.

Did you look at my schematic? I have since made some minor changes.

The 541 is really an input buffer. If you are using it as an output then simply replace it with 8 single open collector gates. I used the 74374 to latch data and then added 8 open collector gates with the IO pins set to BI-DIR. I have a 10K pull-up to 5V.

Also if you are using my schematic then the 74138 select lines that drive the 74374 CLOCK need to be inverted again.

Let me know if this helps.

Andre