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Altera_Forum
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15 years ago

Cyclone III JTAG and AS Configuration

Problem: I am receiving the conf_done pin failed to go high error when trying to program using the JTAG interface. Background: I have configured a custom board to use both AS and JTAG confi...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

No, the nCE pin has two purposes:

- Tri-Stating the FPGA pins connected to configuration memory, when programming it by an external circuit, e.g. the AS connector.

- Disabling the configuration controller in multi-FPGA schemes. As a side effect, JTAG configuration is blocked as well.

The text referring to nCE in the JTAG connector description is somewhat misleading in my opinion. It's actually describing the fact, that pin 6 is used different between older and newer Altera programming adapters. Some older adapters expect pin 6 connected to a supply voltage reference, but it can be unconnected for USB or Byte Blaster.