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USB Blaster, Flex 10KE, EPC2 & JTAG voltage


How should one interpret this document*1 (see attached picture) and it's voltage requirements?

As far as I know, all of the 10KE series pins are 5V tolerant, including JTAG pins, and EPC2 can also work at 5V.

So is this table incorrect, or rather inconclusive, or am I missing something?

Or how exactly would one make a system with a JTAG chain where 10KE requires 2.5V and EPC2 a minimum of 3.3V?

I bet I can run everything at 5V. Or do I really need to have one JTAG for the EPC2 and another for the 10KE? Difficult to believe if that would be the case.

#1: USB-Blaster Download Cable, User Guide

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Answering to my own question, but I think the answer can be deduced from the datasheets.

EPC2 VIH minimum is 2.0V, so it could theoretically be running at 3.3V and a 2.5V JTAG should work with it.

But since the EPF10K datasheet says that all pins are 5V tolerant, and therefore, EPC2 and JTAG can both run at 5V, and the EPF10K will be fine with that.

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Hi there,

Your answer is correct, considering the characteristics of the JTAG chain, as long as the voltage of the JTAG vcc and the pull-up pin is greater than the VIH (min) of all devices on the chain, it can be used normally, and at the same time ensure that the pin voltage is not greater than the device on the chain The maximum withstand value to ensure that there will be no damage to the components on the chain.

Best regards,


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