| 摘要 |
PURPOSE:To realize the single test of a function cell from outside by providing a test bus to secure the input/output of the signal not opened to outside against the outside in a test mode and then setting a test mode. CONSTITUTION:The bidirectional buffers BUF1 and BUF2 whose signal transmitting directions are controlled in both directions by the control signals phi1 and phi2 delivered from a test controller are set between a test bus TBUS and a terminal to which such signals that are directly transferred between the prescribed function cells are supplied. Thus it is possible, for example, to extract the signal supplied to a CRT controller CRTC from a direct memory access controller DMAC to the outside via the TBUS. In addition, the signal needed for the single test can be supplied directly to the controller via the TBUS. |
