半加算回路 （Half Adder; HA)
- 下からの桁上がりがない加算なので、半加算、とよばれる。全加算は、下からの桁上がりも考慮する回路
- 資料23 図2 (C) XORゲートを使用した回路図
- 1ビット同士、A + B を計算させている、と回路をみよう。実行 (run) して、計算結果を確認しよう。
- 真理値表から、半加算回路を設計したことを思い出そう （これくらいなら、閃く）
- A と B → Cは、AND
- A と B → Sは、XOR
- 図3 右の回路に注目。ANDの使い方がうまい。（論理素子が左のものより少ない） ぜひ、描いてみてほしい。
| A |
B |
C |
S |
| 0 |
0 |
0 |
0 |
| 0 |
1 |
0 |
1 |
| 1 |
0 |
0 |
1 |
| 1 |
1 |
1 |
0 |
{
"width":800,
"height":400,
"showToolbox":true,
"toolbox":[
{"type":"In"},
{"type":"Out"},
{"type":"Joint"},
{"type":"DC"},
{"type":"LED"},
{"type":"PushOff"},
{"type":"PushOn"},
{"type":"Toggle"},
{"type":"BUF"},
{"type":"NOT"},
{"type":"AND"},
{"type":"NAND"},
{"type":"OR"},
{"type":"NOR"},
{"type":"XOR"},
{"type":"XNOR"},
{"type":"OSC"},
{"type":"7seg"},
{"type":"16seg"},
{"type":"4bit7seg"},
{"type":"RotaryEncoder"},
{"type":"BusIn"},
{"type":"BusOut"},
{"type":"RS-FF"},
{"type":"JK-FF"},
{"type":"T-FF"},
{"type":"D-FF"},
{"type":"8bitCounter"},
{"type":"HalfAdder"},
{"type":"FullAdder"},
{"type":"4bitAdder"},
{"type":"2to4BinaryDecoder"},
{"type":"3to8BinaryDecoder"},
{"type":"4to16BinaryDecoder"}
],
"devices":[
{"type":"Toggle","id":"dev0","x":104,"y":56,"label":"Toggle","state":{"on":false}},
{"type":"In","id":"dev1","x":168,"y":56,"label":"In A"},
{"type":"Toggle","id":"dev2","x":104,"y":200,"label":"Toggle","state":{"on":false}},
{"type":"DC","id":"dev3","x":24,"y":136,"label":"DC"},
{"type":"XOR","id":"dev4","x":360,"y":64,"label":"XOR"},
{"type":"Joint","id":"dev5","x":296,"y":64,"label":"Joint","state":{"direction":0}},
{"type":"Joint","id":"dev6","x":240,"y":208,"label":"Joint","state":{"direction":0}},
{"type":"Joint","id":"dev7","x":312,"y":192,"label":"Joint","state":{"direction":0}},
{"type":"AND","id":"dev8","x":360,"y":192,"label":"AND"},
{"type":"Joint","id":"dev9","x":256,"y":80,"label":"Joint","state":{"direction":0}},
{"type":"In","id":"dev10","x":168,"y":200,"label":"In B"},
{"type":"Out","id":"dev11","x":456,"y":64,"label":"Out S"},
{"type":"Out","id":"dev12","x":456,"y":192,"label":"Out C"},
{"type":"LED","id":"dev13","x":536,"y":64,"label":"LED S"},
{"type":"LED","id":"dev14","x":536,"y":192,"label":"LED C"}
],
"connectors":[
{"from":"dev0.in0","to":"dev3.out0"},
{"from":"dev1.in0","to":"dev0.out0"},
{"from":"dev2.in0","to":"dev3.out0"},
{"from":"dev4.in0","to":"dev5.out0"},
{"from":"dev4.in1","to":"dev9.out0"},
{"from":"dev5.in0","to":"dev1.out0"},
{"from":"dev6.in0","to":"dev10.out0"},
{"from":"dev7.in0","to":"dev5.out0"},
{"from":"dev8.in0","to":"dev7.out0"},
{"from":"dev8.in1","to":"dev6.out0"},
{"from":"dev9.in0","to":"dev6.out0"},
{"from":"dev10.in0","to":"dev2.out0"},
{"from":"dev11.in0","to":"dev4.out0"},
{"from":"dev12.in0","to":"dev8.out0"},
{"from":"dev13.in0","to":"dev11.out0"},
{"from":"dev14.in0","to":"dev12.out0"}
]
}