| 功能表 | ||
| X1 | X2 | 功能 |
| 0 | 0 | 保持 |
| 0 | 1 | 减计数 |
| 1 | 0 | 加计数 |
| 1 | 1 | 不允许出现 |
根据功能表, 有状态表.
| 状态表 | |||||||
| X2 | X1 | Q1 | Q0 | Q1* | Q0* | Z | 功能 |
| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 保持 |
| 0 | 0 | 0 | 1 | 0 | 1 | 0 | 保持 |
| 0 | 0 | 1 | 0 | 1 | 0 | 0 | 保持 |
| 0 | 0 | 1 | 1 | 1 | 1 | 0 | 保持 |
| 0 | 1 | 0 | 0 | 0 | 1 | 0 | 加计数 |
| 0 | 1 | 0 | 1 | 1 | 0 | 0 | 加计数 |
| 0 | 1 | 1 | 0 | 1 | 1 | 0 | 加计数 |
| 0 | 1 | 1 | 1 | 0 | 0 | 1 | 加计数 |
| 1 | 0 | 0 | 0 | 1 | 1 | 1 | 减计数 |
| 1 | 0 | 0 | 1 | 0 | 0 | 0 | 减计数 |
| 1 | 0 | 1 | 0 | 0 | 1 | 0 | 减计数 |
| 1 | 0 | 1 | 1 | 1 | 0 | 0 | 减计数 |
| 1 | 1 | 0 | 0 | × | × | × | 不允许 |
| 1 | 1 | 0 | 1 | × | × | × | 不允许 |
| 1 | 1 | 1 | 0 | × | × | × | 不允许 |
| 1 | 1 | 1 | 1 | × | × | × | 不允许 |
根据状态表, 得到状态激励表.
| 状态激励表 | |||||||
| X2 | X1 | Q1 | Q0 | D1 | D0 | Z | 功能 |
| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 保持 |
| 0 | 0 | 0 | 1 | 0 | 1 | 0 | 保持 |
| 0 | 0 | 1 | 0 | 1 | 0 | 0 | 保持 |
| 0 | 0 | 1 | 1 | 1 | 1 | 0 | 保持 |
| 0 | 1 | 0 | 0 | 0 | 1 | 0 | 加计数 |
| 0 | 1 | 0 | 1 | 1 | 0 | 0 | 加计数 |
| 0 | 1 | 1 | 0 | 1 | 1 | 0 | 加计数 |
| 0 | 1 | 1 | 1 | 0 | 0 | 1 | 加计数 |
| 1 | 0 | 0 | 0 | 1 | 1 | 1 | 减计数 |
| 1 | 0 | 0 | 1 | 0 | 0 | 0 | 减计数 |
| 1 | 0 | 1 | 0 | 0 | 1 | 0 | 减计数 |
| 1 | 0 | 1 | 1 | 1 | 0 | 0 | 减计数 |
| 1 | 1 | 0 | 0 | × | × | × | 不允许 |
| 1 | 1 | 0 | 1 | × | × | × | 不允许 |
| 1 | 1 | 1 | 0 | × | × | × | 不允许 |
| 1 | 1 | 1 | 1 | × | × | × | 不允许 |
用6片74151和3片非门组成3个16选1数据选择器, 以此实现D0、D1和Z的逻辑表达式.
根据上面的分析, 绘制电路的原理图.