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Honored Contributor
Honored ContributorUnused 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_ForumHonored Contributor
Honored Contributor --- Quote Start --- I have a further question. Suppose one solders a brand new chip onto the PCB. What state would it's pins be in? --- Quote End --- You'll have to read the MAX V handbook. They should be tri-stated, since their function has not been defined. --- Quote Start --- I ask because one of the chip's pins are connected to pull up resistors. If the default state is an output then powering up a brand new chip might cause some I/O damage - but if that is the case, how is one supposed to program it? --- Quote End --- Your pull-up will define the power-on state with a blank device. You can also program the devices prior to assembly. There are TQFP and BGA sockets available. For small numbers of boards, its easier just to use the JTAG to program the boards. Cheers, Dave
