WHAT'S JTAG ?

JTAG is an interface that you can make urself or buy which allow you to erase and reprogram ur receiver's flash rom.Why u should use this JTag?In case of ur receiver become unusable bcoz. of upgrading with wrong software or if you upgrade with wrong method.Meanwhile u need a special software to alive ur receiver again.That's JTag.

JKEYS

jKeys is a program primarily used to access memory on IRDs. It works by utlizing processor diagnostic devices via the JTAG port. This software has been used on STMicroelectronics STiXXXX (ST20 based core) and LSI SC2000 processors.

FLASH ROM

Your receiver flash rom can be erase and program again and again like a CD RW.Uploading wrong firmware into your receiver will not damage your flash rom but only render your receiver useless.If you happen to load the wrong file into your receiver you can use Jtag to reprogram ur flash rom.
If Jtag can read your flash rom , box keys then the flash rom has no problem.It's more safer to use Jtag than to use Null modem cable to upgrade your receiver.

HOW TO BUILT A SIMPLE JTAG CABLE

1.25 Pin Male header (Printer Cable)
2. 4 pieces of 100 ohm resistor
3. 1 piece of 33 ohm resistor
4. 6 pieces of wire (longest 12 inches or as short as possible)

PIN ASSIGNMENT


25 Pin <-------> Receiver
Cable

Pin 2 <-------> Pin 9
Pin 3 <-------> Pin 11
Pin 4 <-------> Pin 13
Pin 5 <-------> Pin 19
Pin 13 <-------> Pin 15
Pin 18 to 25 <-------> Pin 20

Here,down, is the schematic diagram to built a jtag cable for 20 pins.



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