Buffered JTAG and External Power

[dcard2000]

I was using a buffered JTAG without any external power source. But, when I use JKEY to read the TSOP, it kept giving me "Unknown Device" xFFFFFFFF. Could it be caused by not having a power source applied? If I need a power source, what voltage and applied to which pin?

I have a 301.013 with 20-pin JTAG port on the top.

[kelowna_pitboy]

could be. i had the same problem and using a 120v-3volt transformer worked. jtags can be finiky so try it

[dcard2000]

Which pin should I apply the voltage on?

[skinerd]

Which pin should I apply the voltage on?


Pin 20 of the buffer chip is + and of course, ground is -..............Use a couple AA, or C or even D cells.
A buffered jtag will not work without power.

[dcard2000]

I thought pin 18-25 on the DB25 are all ground. Which pin 20 are you referring to?




edited cause I hit edit by mistake...........nothing was changed, except adding this note.

[skinerd]

The buffer chip, the 74hc244n or whatever you are using........18-25 on DB 25 and several on the buffer chip all should be tied together for ground.