GB/T 37979-2019 in English

Analysis of Core Safety Requirements

Key technology implementation points

1. Port instantiation specifications

The standard 5.1.1 clearly stipulates that the name mapping method must be used:

reset_filter_inst: reset_filter port map( reset_in => reset_in, clk => clk, reset_out => reset_out );

The position mapping method is prohibited to avoid maintenance difficulties.

2. Clock domain processing solution

According to the requirements of 5.9.6, cross-clock domain signals must be synchronized:

process(clk) begin if rising_edge(clk) then async_reg1 <= async_signal; async_reg2 <= async_reg1; end if; end process;

Two-level register synchronization can effectively reduce the risk of metastable state.

3. State machine design specifications

5.11.4Recommended three-stage state machine structure:

1. State register migration process
2. Combinational logic state transfer process
3. Synchronous output process

Requires the safety coding attribute: attribute syn_encoding of current_state: signal is "safe, gray";