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Altera_Forum
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14 years ago

Unused CPLD Pins

I have two CPLDs on my PCB that connect to a common SPI bus. In order to keep things simple I'm trying to talk to only one of the chips at first but I'm having some trouble with the voltages which le...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

Hi Dave,

Will remove the resistor and check those. However, considering the short between that and Vcc - no such thing. I checked that multiple times.

What thoughts do you have regarding the bus-contention I spoke of? MISO_Receiver is unused and so set to "output as driving ground" - I am guessing this means it's set to LOW. If that's the case, then surely two signals are trying to driving Pin 1 of the Buffer and this is causing problems. Perhaps this is why the pin is never gets to 3.3V because the other pin isn't Hi-Z.

Would appreciate your thoughts on this.