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Altera_Forum
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14 years ago

JTAG interface

Hello, I would like to interface Cyclone IV JTAG interface via both ways : 1. JTAG USB blaster. 2. FTDI FT2232 MPSSE interface. I am using VCCIO 3.3V in Jtag bank and in figure 8-23 in c...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

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Upon reading your comment, I believe that I will be using instead the SN74LVC244A OCTAL BUFFER/DRIVER WITH 3-STATE OUTPUTS, and have it always enabled with a weak pull up or pull down resistor to set the value. Will this change enable me to drive the JTAG lines correctly?

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This part will be fine.

I'm not sure where you are located, but if you can buy components in the US, the pricing on Mouser for the SN74LVC244A is $0.55 each

http://www.mouser.com/productdetail/texas-instruments/sn74lvc244ansr/?qs=sgaepimzzmuiiwkaiwck2vxqsqozkdecnc%252bi5rnfnoq%3d

whereas the TinyLogic device 512-NC7WZ16P6X is $0.14

http://www.mouser.com/productdetail/fairchild-semiconductor/nc7wz16p6x/?qs=sgaepimzzmuiiwkaiwck2y9zx6ozihaoqc8dih16pqg%3d

I find PCB layout much cleaner using smaller buffers, since you can place them where you need them (and have nice traces).

The 'classic' 244 buffers may be easier to source in other areas of the world though. I just wanted to point out that the smaller parts are not pricey.

Cheers,

Dave