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Altera_Forum's avatar
Altera_Forum
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12 years ago

Cyclone IV AS and JTAG programming at different voltage levels

I have some questions regarding the programming of Cyclone IV devices as shown in figure 8-28 in the datasheet. In my case, the banks where all programming pins reside (1, 2, 5 and 6) are all 2.5V. ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

1. You can get rid of the AS header and all related overvoltage problems by using indirect JTAG programming for the AS configuration device.

2. I prefer 3.3V supply and external schottky clamp diodes with series resistors for the JTAG header. It's quite clear that the 2.5V supply recommendation is a concession to overvoltage sensitivity and the fact, that some Altera programming adapters are driving the JTAG lines with rather low impedance and respective overshoot.

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3. The nCSO and ASDO pins are used for LVDS signals

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With connected AS flash? Doesn't sound like a good idea.