3rd Party/Other Boards and Kits

[brennanwatt]

I am wondering how I could use VHDL to read/write to a specific register on the Atlys Spartan 6. I have been doing some searching on the web and found nothing. Any references or pointers would be appreciated. Thanks!

[eteam00]

I am wondering how I could use VHDL to read/write to a specific register on the Atlys Spartan 6. I have been doing some searching on the web and found nothing. Any references or pointers would be appreciated.

Is this "specific register" internal to the FPGA?  if so, you will need to examine and understand the source code of the design in which this register resides.  You will also need to have a working proficiency in VHDL, as you will probably be modifying the reference design source code.

Some FPGA development boards include a system "monitor" function for accessing internal FPGA registers from a "console window" application running on a host computer.  If such cases, you do not need to modify VHDL source code.

Does this make sense?

-- Bob Elkind

[brennanwatt]

I have been using FPGALink: http://www.makestuff.eu/wordpress/?page_id=1400 to have the board communicate with a PC. this software allows me to read and write registers from the command line. However, I want the Atlys to read in values from the VHDCI port, store them into an onboard register, and then read them out from the command line.

[eteam00]

However, I want the Atlys to read in values from the VHDCI port, store them into an onboard register, and then read them out from the command line.

Does this logic already exist in the FPGA design, or is this code which you need to write?

-- Bob Elkind

[brennanwatt]

I already have the ability to read/write using FPGALink. I also know how to get data from the VHDCI pins. I don't know how to write code for the FPGA (VHDL bit file) that will take a value and store it in the registers of the FPGA (so that it can be read using the FPGALink code)

[joelby]

It may be better to discuss this problem on the FPGALink mailing list, since it's not a Xilinx-specific problem.

Anyway, you will need to fiddle with FPGALink's TopLevel.vhdl file. Have a look at the switches and LEDs for an example of how to read and write a register. You can add additional registers by adding cases to the "case addr" statements in STATE_WRITE (which is writing from the FPGA to the PC) and STATE_READ (which is reading from the PC to the FPGA).

If you only had one read register and one write register and didn't care about switches and LEDs, you can just hook these up to the led_out and sw_in signals.

Note that because the TopLevel module is synchronous to the FX2LP's IFCLK, you will need to consider clock domain crossing issues if the rest of your design is using the system clock or something else.