Unexpected clock edge specification

Sigasi can check that the same clock edge specification style is used throughout the entire design. This standard rule provides a clean coding style guaranteeing consistency in clock checks. This rule consists of three configurable options:

event attribute, ensures that all clock conditions are using the event attribute, for example, clk'event and clk = '1'
stable attribute, ensures that all clock conditions are using the stable attribute, for example, not clk'stable and clk = '1'
edge function (the default), ensures that all clock conditions are using an edge function, for example, rising_edge(clk) falling_edge(clk)

Example with “edge function” selected

VHDL
process(clk) is
    variable count : natural := 0;
begin
    if clk'event and clk='0' then -- Wrong clock style!
        count := count + 1;
    end if;
end process;

VHDL
process(clk) is
    variable count : natural := 0;
begin
    if falling_edge(clk) then
        count := count - 1;
    end if;
end process;

Note that using clock attributes is deprecated since VHDL 93 by the IEEE 1164 standard, use edge functions instead.

Rule configuration

This rule can be disabled for your project, or its severity and parameters can be modified in the project linting settings. Alternatively, it can be manually configured using one of the following templates, depending on the type of project you use.

For Modular Projects, add these entries to your project's .sigasi/settings.json settings file. To scope the settings to a specific folder or file instead of the whole project, place them inside an @override block; to scope them to a specific target, place them inside a @targets block.
JSONC
```
{
    "vhdl.rules.250.severity": "{ERROR|WARNING|INFO|IGNORE}",
    "vhdl.rules.250.parameters.style": "{EDGE_FUNCTION|STABLE_ATTRIBUTE|EVENT_ATTRIBUTE}"
}
```
For Classic Projects, add the VHDL lines to .settings/com.sigasi.hdt.vhdl.linting.prefs and the Verilog/SystemVerilog lines to .settings/com.sigasi.hdt.verilog.linting.prefs:
PREFS
```
250/severity/${path}={error|warning|info|ignore}
250/params/style/${path}={EDGE_FUNCTION|STABLE_ATTRIBUTE|EVENT_ATTRIBUTE}
```