Hardware interview practice

Verify a word-path search peripheral

MediumReference ModelsSystemVerilog

Write the path oracle and transaction checks for firmware driving a memory-mapped I/O (MMIO) peripheral that finds the first nonrepeating path spelling an uppercase word in an 8x8 board.

Starting point

Question code

typedef struct packed { byte unsigned row, col; } coord_t;

function automatic bit first_word_path(
  input byte unsigned board[8][8],
  input int rows, cols,
  input byte unsigned word[$],
  ref coord_t path[$]
);

Reviewed example

Work through one case

Input

board 2x3=[[A,B,C],[D,E,F]]; word="ABE"

Expected output

found=1; first path=[(0,0),(0,1),(1,1)]

Row-major start order selects A, then the required up-right-down-left neighbor order reaches B and E without reusing a cell.

What to cover

Requirements

Validate dimensions, word length, active uppercase bytes, and address arithmetic before START; allow a null path when only status is requested.
Copy inputs at accepted idle START, try start cells in row-major order, and visit neighbors up, right, down, then left; the first full path wins.
Apply the stated invalid-setting precedence, produce a bounded error completion with zero path, and reject configuration writes while busy.
Keep completed status and path stable until the next accepted job or reset; IRQ clear changes only the interrupt, and reset cancels all work.