Know the Operation
The RAM memory system shown in Figure 11-42 will be used in our examples. As
we emphasized in earlier discussions, successful troubleshooting of relatively
complex circuit or system begins with a thorough knowledge of its operation. Before we can discuss the testing of this RAM system, we should first analyze it carefully so that we fully understand its operation.
The total capacity is 4K x 8 and is made up of four 1K x 8 RAM modules. A module may be just a single IC, or it may consist of several ICs(e.g two 1K chips). Each module is connected to the CPU through the address and data busus and through the R/W control line. The modules have common I/O data lines. During a read operation these lines become data output lines through which the selected module places its data on the bus for the CPU to read. During a write operation, these lines act as input lines for the memory to accept CPU-generated data from the data bus for writing into the selected location.