addrmap top {

    reg {
        field {
            sw=rw; hw=na;
            onread = rclr;
        } f1[7:0] = 0xF0;

        field {
            sw=rw; hw=na;
            onread = rset;
        } f2[15:8] = 0x0F;
    } r1;


    reg {
        field {
            sw=rw; hw=na;
            onwrite = woset;
        } f1[3:0] = 0x0;

        field {
            sw=rw; hw=na;
            onwrite = woclr;
        } f2[7:4] = 0xF;

        field {
            sw=rw; hw=na;
            onwrite = wot;
        } f3[11:8] = 0x0;
    } r2;

    reg {
        field {
            sw=rw; hw=na;
            onwrite = wzs;
        } f1[3:0] = 0x0;

        field {
            sw=rw; hw=na;
            onwrite = wzc;
        } f2[7:4] = 0xF;

        field {
            sw=rw; hw=na;
            onwrite = wzt;
        } f3[11:8] = 0x0;
    } r3;

    reg {
        field {
            sw=rw; hw=na;
            onwrite = wclr;
        } f1[7:0] = 0xF0;

        field {
            sw=rw; hw=na;
            onwrite = wset;
        } f2[15:8] = 0x0F;
    } r4;
};