29-10-2018, 10:54 AM
Unfortunate to find a duff decoder chip. Recently I was dealing with an Aurora that was suspected of having a lazy 14.318MHz xtal or possibly even a faulty decoder chip. As it happens, that was a misdiagnosis. I was guiding the owner through diganosis, he had a good scope with good x10 probes. The results can be misleading even with x10 probes unless you understand their effect on the circuit under test. Ultimately the fault was a regulator chip giving false "power good" indications which inhibited the Xilinx FPGA from booting.
Frank, an x1 probe is not good enough. It presents a load of around 100pF, more than enough to upset the operation of many circuits. Even x10 probes can give misleading results. In high speed logic (Hedghog is fairly high speed) the type of probe and use of the probe's ground lead can matter a lot.
Frank, an x1 probe is not good enough. It presents a load of around 100pF, more than enough to upset the operation of many circuits. Even x10 probes can give misleading results. In high speed logic (Hedghog is fairly high speed) the type of probe and use of the probe's ground lead can matter a lot.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
