Verilator

Obviously not synthesizable but useful for testbenches and behavioral models.

Example:

typedef enum {
        DDR_CMD_TYPE_PRECHARGE,
        DDR_CMD_TYPE_ACTIVATE,
        DDR_CMD_TYPE_WRITE,
        DDR_CMD_TYPE_READ,
        DDR_CMD_TYPE_REFRESH,
        DDR_CMD_TYPE_NOP,
        DDR_CMD_TYPE_MRS,
        DDR_CMD_TYPE_DES,
        DDR_CMD_TYPE_ZQC,
        DDR_CMD_TYPE_ERROR
} DDR_CMD_TYPE;

DDR_CMD_TYPE write_command_queue[$];