| 摘要 |
A TRISTATE CIRCUIT FOR DRIVING THREE SIGNAL LEVELS TO A PIN OF A DEVICE-UNDER-TEST IS DISCLOSED. THE TRISTATE CIRCUIT INCLUDES A DRIVER HAVING AN OUTPUT AT A FIRST SIGNAL LEVEL AND ADPATED FOR COUPLING TO THE PIN. A FIRST SWITCHING UNIT COUPLES TO THE OUTPUT AND RESPONDS TO A PROGRAMMED SIGNAL. THE FIRST SWITCHING UNIT OPERATES TO SELECTIVELY ALTER THE FIRST SIGNAL LEVEL TO A SECOND SIGNAL LEVEL. A SECOND SWITCHING UNIT CONNECTS SERIALLY TO THE FIRST SWITCH. THE SECOND SWITCHING UNIT RESPONDS TO A SECOND PROGRAMMED SIGNAL AND OPERATES TO COOPERATE WITH THE FIRST SWITCH TO ALTER THE SECOND SIGNAL LEVEL TO A THIRD SIGNAL LEVEL. |
