vT1C
via_reg(VIA1, vT1C) = CLK_INTL;
via_reg(VIA2, vT1C) = (profint - 1) & 0xff;
via_reg(VIA2, vT1C) = 0;
via_reg(VIA1, vT1C) = 0; /* 1024 clock ticks */
via_reg(VIA1, vT1C) = 0;
via2_reg(vT1C) = 0;