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4. The receiving module senses the DR signal and reads the data from the Bus.

5. The receiving module puts a Bus DATA ACCEPTED\DA signal on the Bus.

6. The Kbus module senses the DA signal and passes it on to all Ke module operation-complete inputs as the Bus DONE signal. Only the most recently evoked Ke responds to this signal.

Drawing boxes around modules in the RTM system diagrams is pretty, but the boxes are not really necessary. Furthermore, the slashed control lines linking the K part of the system to the DM part of the system can be inferred from the notation that accompanies each K module. Thus, throughout the rest of the book we shall draw RTM system diagrams as shown in Figure 15, which is the compact version of Figure 6. Notice that the K(serial merge)\Ksm is drawn simply as a merging of control arcs. Also, the Kb2 module reads I = 0 instead of BSR = 0, since this is a better description of the condition being tested.

Fig. 15. RTM system diagram (compact) of Fig. 6.



In this section we present descriptions of the remaining Register Transfer Modules. Block diagrams of all RTM modules are given in Figure 16. We encourage the reader to use these block diagrams as module ready references. For the K modules, which are used to specify flowcharts, three types of notation are shown. The first is the PMS boxed form with signals, which we have used for clarity in most of the examples in this chapter. The second is the unboxed (explicit) form of notation, in which we have just removed the boxes, as was done in the example of Figure 15. in the third notation, unboxed (implicit), we also remove the PMS type designations from the statements, because they can be inferred from the flowchart and a knowledge of RTM's. We use the second and third notations throughout the remainder of this book.

The block diagrams of Figure 16 describe the modules at the RT level. In the


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