| 摘要 |
PURPOSE:To facilitate the tests given to the peripheral equipments by using a control means which fixes all input/output pins in the high impedance state excepting a single input/output pin in response to the prescribed signal supplied to said single pin. CONSTITUTION:The 3-state buffer groups 14 and 15 are connected between a group 12 of general-purpose input/output pins and a main body internal circuit. A signal of a high level is supplied to a special input pin 13 when a test is given to a peripheral equipment. This high-level signal functions to fix the exclusive group 15 in a high impedance state. At the same time, the general-purpose data output buffer group 14 is also fixed in a high impedance state via a 2-input OR gate 16. |
