Writing SystemVerilog

Naming Conventions

• Modules: svc_ prefix (e.g., svc_arbiter)
• Clock: Always clk
• Reset: Always rst_n (active-low)
• Next-cycle signals: _next suffix (e.g., grant_valid_next)
• Pipeline stages: _p1, _p2 suffixes
• Interfaces: s_ for subordinate, m_ for manager
• Valid/ready: Use valid/ready for stream interfaces
• Multi-cycle ops: Use start/done

Comment Style

• NEVER use end-of-line comments - ALL comments on line above
• Use blank comment separators for sections:

//
// Write pointer logic
//

Signal Declarations

• Use logic instead of wire/reg
• Declare each signal on separate line, never group
• Align signal widths for readability:

logic [  ADDR_WIDTH:0] ptr;
logic [DATA_WIDTH-1:0] data;

Code Structure Order

1. Localparams
2. Internal signals
3. Child module instantiations
4. Combinational logic (always_comb)
5. Sequential logic (always_ff)
6. Formal assertions (if applicable)

State Machines

• Use typedef enum without explicit bit width
• Prefix states with STATE_ (or READ_STATE_/WRITE_STATE_ for multiple FSMs)
• Separate always_ff for transitions, always_comb for outputs

typedef enum {
  STATE_IDLE,
  STATE_BUSY,
  STATE_DONE
} state_t;

Reset Pattern

Always use synchronous active-low reset:

always_ff @(posedge clk) begin
  if (!rst_n) begin
    counter <= '0;
    state   <= STATE_IDLE;
  end else begin
    counter <= counter_next;
    state   <= state_next;
  end
end

Assignments

• Use always_ff with non-blocking (<=) for sequential logic
• Use always_comb with blocking (=) for combinational logic
• For complex conditionals, prefer if/else over ternary operators

Unused Signals

Use the SVC_UNUSED macro:

`SVC_UNUSED({signal1, signal2, signal3});

After Writing Code

Always run:

• make format - format code
• make lint - check for errors

For full details see docs/style.md