Signature Analysis Testing of a Direct Memory Access Controller
Original Publication Date: 1983-Jan-01
Included in the Prior Art Database: 2005-Feb-06
Signature analysis is a useful test technique for verifying the proper operation of cards and troubleshooting faulty cards to determine where the problem resides. In that manner, many cards may be salvaged with simple repair. However, tests utilizing the signature analysis technique are not possible where feedback paths are present. For example, in the case of direct memory access (DMA) chips, the DMA controller is connected to peripheral chips via request and acknowledge lines for one type of feedback and a second type of feedback is found between the DMA controller and the CPU via hold request and hold acknowledge signals. This article describes a combined hardware and software solution to break these feedback loops and make them more testable.