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Altera_Forum
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18 years ago

JTAG configuration protocol specification

Hello, We're in the process of debugging a JTAG configuration problem (Quartus doesn't recognize the chain that consists of a single CycII device). We try to look at the TDI, TMS, TCK, TDO line...
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Altera_Forum
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18 years ago

Checking the chain continuity is a very basic JTAG operation, not specific to Altera devices in any way. The JTAG access algorithm is described in various Altera documents (and a nearly inifinite amount of internet resources).

Not recognizing the chain means that one of the four signals is either unconnected, wrongly connected or shorted. Almost easy to grasp to my opinion. Another possible issue is a missing or out-of-specification supply, e. g. missing 2.5 V VCCA at a Cyclone III device.