[IC design] Google interview design verification, Systemverilog constraint and memory read part two
以下的題目皆是需要使用 systemverilog 來實現
Q1. Give a constraint to allocate 4 memory blocks in 4KB memory.
Ans:
class Allocate_mem;
rand bit [12:0] start_addr[4];
rand bit [12:0] size[4];
constraint c_total_size {
size.sum() with (int'(item)) <= 4096;
}
constraint c_no_overlap {
foreach(start_addr[i]) {
if(i != 3)
start_addr[i+1] >= start_addr[i] + size[i];
else
4096 >= int'(start_addr[i] + size[i]);
}
}
endclass
Q2. Give a function to find out N byte continuous memory in 1 KB memory, if it finds enough memory space then return the start address, if not,this function should return -1
How to check this address it available? if this address value is not equal to 0, it means it's not available?
Ans:
mem[1024];
function getMem(int N);
int cnt = 0;
int cur_addr = 0;
while(1) begin
if( mem[cur_addr] == 0) begin
cnt = 1;
while(1) begin
if( mem[cnt+cur_addr] != 0) begin
break;
end else if (cnt == (N-1)) begin
return cur_addr;
end
cnt = cnt + 1;
end
end
end
return -1;
endfunction
