FPGA Memory - Accessing 'Free' Registers

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FPGA Memory - Accessing 'Free' Registers

Post by lw58 » Wed Aug 05, 2015 4:30 pm


I am trying to make use of the FPGA registers in the 'FREE' range from 0x40600000 to 0x406FFFFF. I have tried to write to the registers using the monitor utility, however I find that I cannot change the value on the registers. How can I obtain read/write access to these registers?


Nils Roos
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Re: FPGA Memory - Accessing 'Free' Registers

Post by Nils Roos » Wed Aug 05, 2015 5:53 pm


There are no registers to be found in that address range. All address locations from 0x40600000 to 0x406fffff are tied to a constant zero on read and to nothing on write.
The following piece of Verilog code from red_pitaya_top.v takes care of that:

Code: Select all

assign sys_rdata[ 6*32+31: 6*32] = 32'h0;

assign sys_err[6] = {1{1'b0}} ;
assign sys_ack[6] = {1{1'b1}} ;
If you want to access registers under those addresses, you will have to provide them first.

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