The meaning of schematic analysis is to obtain the hardware resources, interfaces and pin connection relationships used by various memories and peripherals by reading the schematic diagram of the circuit board. To understand the hardware composition of the entire circuit board as a whole, the analysis method of the schematic diagram is to radiate from the main CPU to the memory and peripherals, and the steps are as follows.
1) Read the CPU section to know which chip selects, interrupts and integrated peripheral controllers of the CPU are in use, and list these elements a, b, c,. When there are many CPU pins, the chip may be divided into several modules and drawn separately on different pages of the schematic diagram. At this time, the corresponding parts should be analyzed in place.
2) For the elements listed in step 1, analyze the actual usage from the corresponding peripherals and memory circuits in the schematic. The hardware schematic contains the following elements.
symbol. The symbols describe the peripheral pins of the chip and the signals of the pins. For complex chips, they may be divided into several symbols. In the symbol, the pins belonging to the same signal group are generally arranged together. Figure 2.22 shows the symbols of NOR Flash AM29LV160DB and NAND Flash K9F2G08.
Figure 2.22 Symbols in the schematic
network (net). Describe the interconnection between chips, connectors and separate component pins. Each network needs to be given a suitable name according to the definition of the signal. If no name is given to the network, the EDA software will automatically add a default network name. The AM29LV160DB after adding the network is shown in Figure 2.23.
Figure 2.23 Network in Schematic
describe. Some text will be added to the schematic diagram to help describe the schematic diagram (similar to the comments in the source code). For example, the footer of each page will have a functional description of the page. For important signals, the corresponding symbols and networks in the schematic diagram will also be included. With text description.