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Altera_Forum
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14 years ago

Can Cyclone IV JTAG VCC use separate 2.5V instead of VCCA?

The Cyclone IV handbook in section 8-47 says: --- Quote Start --- For device using VCCIO of 2.5, 3.0, and 3.3 V, refer to Figure 8–23. All I/O inputs must maintain a maximum AC volt...
Altera_Forum's avatar
Altera_Forum
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14 years ago

The said Rev. B USB Blaster had been equipped with a rather low series resistor (10 ohm or so). And shipped with a special flex print cable with low characteristic impedance. This moved the impedance matching problem to the JTAG connector, but didn't solve it. And the flex cable was often replaced by a regular IDC cable, because the original cable broke easily and was too short or to rigid in many cases.

Newer USB Blasters and the present Terasic model have less overshoot as far as I'm aware of.