DescriptionQ1040
Q1040DVASIC interview problem
Constrain exactly three nonoverlapping 110 patterns
TechniquesSystemVerilogPattern constraintsExact count
DifficultyHard
TopicConstraints
LanguageSystemVerilog
Requirements4 checkpoints
01
Problem
Randomize a 32-bit word containing exactly three nonoverlapping 3'b110 windows when every possible three-bit sliding window is counted.
Starting declarationSystemVerilog
rand bit [31:0] value;
rand int unsigned pos[3];Example input and output
Use this case to check your interpretationInput
selected starts = {0, 3, 6}; value = 32'h0000_01B6Output
legal: value[0 +: 3], value[3 +: 3], and value[6 +: 3] are the only 3'b110 windowsExplanation
The low nine bits are three adjacent 110 groups. Windows starting between those groups differ from 110, and the remaining upper bits are zero.
02
Requirements (4)
- Sort three selected start positions inside 0 through 29.
- Keep selected starts at least three bits apart.
- Force each selected indexed part-select to equal 3'b110.
- Force every unselected three-bit window to differ from 3'b110.