DEFINING DESIGN RULES
Design rules are a series of conventions that are established to account for physical constraints in a system and to make drawings and documentation understandable to all design team members. These rules should be written out and copies should be given to all members of the design team (if one exists).Design rules also help new design team members to quickly familiarize them-selves with the project if they enter late in the program.
You must first define how documentation will be written. Large systems require many drawings. You must specify how signals will be passed from one drawing to another. For simple systems with just a few drawings, a circle can represent a signal that goes to another page. For larger systems in which many drawings are used, a notation indicating to which drawing the signal goes and from which drawing it comes is necessary, Signals that go to a card's edge can be represented by another symbol-perhaps a triangle or, more conventionally, a pointed tab as shown in Fig. 6-1.
It is also a good practice to give all signals and components names. This makes explanations and references in discussions and documentation less con-fusing. By assigning functional names to system components such as “memory control ROM” or “output selection decoder,” it will be easier to relate the detailed schematics to the overall system block diagram. In the case of naming signals, shorter abbreviated names are preferable. An 8-bit data input bus might be given the name DI0 through DI7.