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Altera_Forum
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13 years ago

Cyclone IV E JTAG inputs board pull-up to VCCA instead of VCCIO?

Shouldn't Cyclone IV E JTAG inputs be pulled up on the board to VCCIO (3.3V in our case) instead of VCCA (2.5V) as recommended in the pin connections guidelines? The device handbook says "all the JTA...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

Hi,

I've implemented the guideline to pull TMS and TDI to VCCA (as shown in 8-23 and required for 2.5, 3.0 and 3.3V I/O) which is a well working combination.

Your question on I/O levels is answered in "Configuration and JTAG Pin I/O Requirements" (p.8-5): "Cyclone IV devices are manufactured usingt the TSMC 60nm low-k dielectric process. Although Cyclone IV devices use TSMC 2.5-V transistor technology in the I/O buffers, the devices are compatible and able to interface with 2.5, 3.0 and 3.3-V configuration voltage standards..."

(For JTAG the VCCA is to be connected to the Header and is used by the USB-Blaster as I/O supply...)