BS 5070-4:1990 pdf free.Engineering diagramdrawing practice Recommendations for logic diagrams.
BS 5070-4 Rules for the use and combination of symbols for binary logic elements are given in BS 3939-12.Symbolsrepresenting hardware elements which are contained in one physical package may also be combined
providing the interconnections are not accessible to the user and the quoted rules are applied.
Each logic element should be shown by that symbol which correctly depicts the logic function actuallyperformed by that element in the system.
The preferred orientation of symbols is for inputs to be on the left and outputs to be on the right. However,alternative orientations are permissible, as shown in Table 1, providing the following rules are observed.a) The rules for the placement of the qualifying symbol(s) for the device function should be obeyed (seeBS 3939-12).
b) In general, outputs should appear on the opposite side of the symbol outline from the inputs.c)Sufficient space should be provided to avoid confusion between the qualifying symbol(s) for thefunction and the input and output labels.
d) Strings of characters, forming qualifying symbols or labels, should preferably appear in normalreading order and each input (output) label should be centred with respect to its input (output) line.e) The orientation of qualifying symbols for negation, polarity, grouping dynamic inputs, inhibit andamplification with respect to the connection lines should remain unchanged.
f) Where the signal flow is from right to left or from bottom to top, directional arrows should be used onthe signal line.
Symbols for complex logic units should be developed in accordance with the rules given in BS 3939-12.Ifthis is not possible owing to the complexity of the function, then the symbol used can be a simple rectanglecontaining a description of the function or a reference to the appropriate documentation. Uniform labelsshould be used for inputs and outputs where possible.
If a symbol for a complex function has to be repeated on a diagram each repetition may be shown as a simplerectangle with appropriate references.
Any elements of a multiple package which are not used,e.g.inputs or outputs or complete elements withina multiple package, may be shown. When shown it is important to identify the unused elements and thecorresponding pin numbers.BS 5070-4 pdf download.