Fig. 9. RTM Bus signals.

RTM system, so they must be transduced. Examples are signals from analog devices, Teletypes, modems, lights, switches, etc. Figures 2 to 6 used ( ^{____ _ __ __} ), but in subsequent chapters these will be shown merely as _______ .

To summarize, in subsequent chapters only two types of links will usually be differentiated graphically: the RTM Bus (shown ^_____ or ====), and all other links ( ^____ ). Normally the differences in these latter links is easily seen by the context. Generally, the signal names will be labeled on top of the 'links.

Physical Implementation of RTM's

The physical implementation of RTM's depends on the technology being employed. The current DEC PDP-16 modules are constructed using medium scale integrated circuits mounted on double sided printed circuit boards of 5" x 8 1/2" with 72 pins (double height, extended length) or 2 1/2" x 8 1/2" with 36 pins (single height, extended length) or 2 1/2" x 4 1/4" with 36 pins (single height, standard length). A few RTM's, e.g., the DMgpa, are actually two of these boards; these require board connectors on the top and back of the printed circuit boards. Some RTM primitives, e.g., the Kevoke's, are so small that several are placed on a single height printed circuit board. The boards can be plugged into the back of 5 1/4" x 8 1/2" x 19" wirable panels, which contain a prewired Bus. The panel is plugged into a mounting rack which usually contains a power supply.

Logical Level - Voltage Level Conventions. In Chapter 7, we discuss the switching circuit level design of RTM's. At the RT level, which we are presently discussing, it is generally unnecessary for the reader to know the actual voltages that correspond to logic signals. However, we present them here for completeness. Detailed information is available in the PDP-16 handbook.

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