Data transmission and display

Abstract

We have assumed so far that digital signals are not affected when transmitted from one integrated circuit to the next. However, the effect of the interconnecting lines, particularly on the steep signal edges, may be significant. As a general rule, the simple connecting wire is no longer adequate if the time delay along that wire is in the same order of magnitude as the rise time of the signal. Such connections should therefore have a maximum length of about 100 mm for each nanosecond of rise time. If this limit is exceeded, serious pulse deformations, reflections and oscillations are incurred. These disturbances can be avoided by the use of lines having a defined characteristic impedance (coaxial line, microstrip line). The line is then terminated by its characteristic impedance which usually has a value between 50Ω and 300Ω.