YosysHQ.yosys/techlibs/nanoxplore/rf_rams_l.txt

ram distributed $__NX_RFB_L_ {
    abits 6;
    width 16;
    cost 10;
    init no_undef;
    prune_rom;

    port sw "W" {
        clock anyedge;
    }
    port sr "R" {
        clock anyedge;
        rden;
    }
}