De2-115 windows application to control Cyclone chip

Hi Dave,

Here is my very basic knowledge at this points about Jtag,

Please see if I am writing something wrong:

1. Jtag- is an interface, was invented in order to enable boundary (chip cells output) - scan, for debug, for reading data out, and for enabling data in

2. The basic concept is that data moves like in shift register, using shift register, that enable to "move data" in and out

3. There is an option to connect many chips in serial and move data between them (I think up to 128 chips), but I mind about 1 only :)

4. The basic JTAG signal (control the Jtag) are generally only 4 (sometime 5) - which are: CLK, TDI, TDO, TMS

5. if we enter JTAG mode, than the chip enter into JTAG mode, and not working like Usual (since we have a mux that enable at this stage data in or data out)

6. Basically to enter JTAG command -> use just CLK and TMS (of corse need the IR and DR registers data also)

7. The Jtag has only 2 registers: IR - for Instructions, DR - for DATA (that is all!)

8. The Length of IR - determine the Max commands we might have (e.g. 3 bits IR - is only 8 commands)

9. The DR is enabling the DATA in/out

This is very basic to start working

Is something that is written wrong here?

Thanks,

Roee