56 : r; break;
              case 0xE: /* SHL */ flag(this.v[x] & 0x80); this.v[x] = (this.v[x] << 1) % 256; break;
              default: unknown(instr); break;
            }
          break;
          case 0x9: /* SNV */ if (this.v[x] != this.v[y]) { this.pc += 2; } break;
          case 0xA: /* MEM */ this.i = a; break;
          case 0xB: /* JMR */ this.jump((this.memory[a] << 8) | this.memory[a+1]); break;
          case 0xC: /* RND */ this.v[x] = Math.floor(Math.random() * 255) & n; break;
          c