hi every body
it's a cool project that you can build yourself!
if you google the jtag ice subject you will find a lot of web pages that build jtag ice clone but here you will see how to build jtag twice(stk500 + jtag ice)

1-first of all we will use the same schematic of jtag ice.

2-we will use jtag boot to upgrade our Atmega16.

3-program your Atmega16 with boot.hex then start avr studio and  from tools menu
choose avr prog then find the upgrade.ebn in jtag ice folder of your avr studio
for example C:\Program Files\Atmel\AVR Tools\JTAGICE.

4-we will read back Atmega16 flash with another programmer and confirm the last 
code address in this example the address is 0x2d2d
then open the hex file with note pad and delete the line that start whit :103800000C942A1C0C94471C0C94471C0C94471CC9
and delete following lines till :00000001FF do not delete :00000001FF line
and save the file.

5-once again program your chip first erase it and program it with new file.

6-we will set the start address of our stk500 firmware that i was written once 
jtag last byte + some words
change the following line in makefile
LDSECTION  = --section-start=.text=0x2da0

7-then compile the stk500 code and program the chip with out erasing it!

8-then we will use the following code in assembler and set the fuse byte to SMALLBOOTSTART.
in this code we will decide to choose between stk500 or jtag ice respect to pinc.6
if pin==0 then start stk500
else start jtag ice.

9-again we will program the chip without erasing it and using asm.hex.

10-in stk500 you can add a led to PORTB.2 for showing communicationsand stk500 pins is as follow
sck	sck pin		of Atmega16
miso    miso pin        of Atmega16
mosi  	mosi pin  	of Atmega16
reset  	portb.1  	of Atmega16
led 	portb.2  	of Atmega16
now you have a cool tool to use.

for those of you who live in Iran if you could not build the project contact me and
i will sell you the complete project with PCB.
my mobile 009809177154367
address: Iran Shiraz P.O.box 71765-385

project files