A memory is of size 8192 bytes and it is byte addressable. I need to generate 3 different start and end addresses within this memory space. Each of these 3 sub areas can be a min of 1 byte and a max of 8192 bytes. These need to be non overlapping.
I have tried creating a size variable and start addr variable with solve before constraint for size before address. This is not working for me.
Any help in creating a constraint for this is appreciated.
In reply to kernalmode1:
class address;
int N = 3;
int memLimit = 8192;
rand bit [15:0] addrs[];
rand bit [15:0] sizes[]
function new;
addrs = new[N];
sizes = new[N]
endfunction
constraint c{
foreach(addrs[Range]) {if (Range != N-1)
addrs[Range] + sizes[Range] < addrs[Range+1];
else
addrs[Range] + sizes[Range] < memLimit;
sizes[Range] inside {[1:memLimit-1]};
}
endclass
In reply to dave_59:
Thanks Dave.
class address;
int N = 3;
int memLimit = 8192;
rand bit [15:0] addrs[];
rand bit [15:0] sizes[];
function new();
addrs = new[N];
sizes = new[N];
endfunction
constraint c {
foreach(addrs[Range]) {
if (Range != N-1)
addrs[Range] + sizes[Range] < addrs[Range+1];
else
addrs[Range] + sizes[Range] < memLimit;
sizes[Range] inside {[1:memLimit-1]};
}
}
endclass
module top;
initial begin
address fc;
fc = new();
repeat(10) begin
fc.randomize();
$display("%p %p", fc.addrs, fc.sizes);
end
end
endmodule
In reply to dave_59:
In reply to kernalmode1:
class address;
int N = 3;
int memLimit = 8192;
rand bit [15:0] addrs[];
rand bit [15:0] sizes[]
function new;
addrs = new[N];
sizes = new[N]
endfunction
constraint c{
foreach(addrs[Range]) {if (Range != N-1)
addrs[Range] + sizes[Range] < addrs[Range+1];
else
addrs[Range] + sizes[Range] < memLimit;
sizes[Range] inside {[1:memLimit-1]};
}
endclass
Hi Dave,
What is “Range” variable here?
In reply to seenu:
It is the foreach loop iterator variable.
I am getting these as my results
'{'hfe6a, 'hf38c, 'h1092} '{'h523, 'he62, 'h808}
doesn’t this exceed 8192 bytes - 'hfe6a + 'h523 = 66445(in binary greater than 8192?) I think my understanding is wrong please help
Good catch. Remove the else in the constraint, or simply write
constraint c {
foreach(addrs[Range]) {
if (Range != N-1)
addrs[Range] + sizes[Range] < addrs[Range+1];
addrs[Range] + sizes[Range] < memLimit;
}
}
program p1;
class c1;
parameter int N=3;
int memlimit = 8192;
rand bit [15:0] addr[];
rand bit [15:0] size[];
function new;
addr = new[N];
size = new[N];
endfunction
constraint c1{
foreach (addr[range]){
if(range!=N-1)
addr[range]+size[range]<addr[range+1];
addr[range]+size[range]<memlimit;
}
}
function void post_randomize();
$display("memory 8192 details %0p", obj);
endfunction
endclass
c1 obj;
initial begin
obj = new;
repeat (1)
obj.randomize();
end
endprogram
output of the above code is
memory 8192 details
'{memlimit:8192, addr:'{'h100b, 'h1014, 'h1d75}, size:'{'h2, 'h8a6, 'h177}}
Total memory size is 8192 (8KB).
But when I add sum of all sizes, its not 8KB.
Do I need to add one more constraint like this?
size.sum()==8192
I need to understand how above code is forming 8KB, could someone please point?
Thank you,
I think so that the questions asks to generate 3 different space under 8129 bytes boundary , it doesn’t mean that you have to have different space such that it sums to the memory space.
@atalur you can give some clarity on this!
class mem_blocks;
int num = 4;
parameter int mem_boundary = 4096;
rand bit [12:0] sizes;
// 13-bit to hold up to 4096
rand bit [12:0] memory;
function new();
memory = new[num];
sizes = new[num];
endfunction
constraint memory_c {
sizes.size() == num;
memory.size() == num;
// First block starts at 0
memory[0] == 0;
foreach (memory[i]) {
// Each size is 1024 (swap with inside{[1:...]} for random)
sizes[i] inside {[1:mem_boundary-1]};
// Contiguous: next block starts exactly where this one ends
if (i < num - 1)
memory[i+1] == memory[i] + sizes[i];
}
// Last block ends exactly at boundary
memory[num-1] + sizes[num-1] == mem_boundary;
}
function void print();
foreach (memory[i])
$display("addr[%0d] = %0d,\tsize = %0d -> ends at %0d",
i, memory[i], sizes[i], memory[i] + sizes[i] - 1);
$display("Total size = %0d bytes", sizes.sum());
endfunction
function void post_randomize();
$display("--- Randomization Successful ---\n");
print();
endfunction
endclass
module testbench;
initial begin
mem_blocks blk = new();
blk.randomize();
end
endmodule
-– Randomization Successful —
addr[0] = 0, size = 660 → ends at 659
addr[1] = 660, size = 1131 → ends at 1790
addr[2] = 1791, size = 847 → ends at 2637
addr[3] = 2638, size = 1458 → ends at 4095
Total size = 4096 bytes