previous | contents | next

Fig. CD-3. Module diagram for K(programmable delay).



KEYWORDS: Wait-until, ERTM, polling, synchronization, parallel merge

Conceptually the notion of waiting for a Boolean condition to occur (to be true) prior to proceeding is fundamental to synchronization between systems. Normally some external process causes a Boolean (flag) to be set to indicate the occurrence of an event. A second process, which is to be synchronized with the event, checks the Boolean input condition by polling, and when true, proceeds.


Design a module, ((wait-until), which carries out the waiting function with external characteristics as shown in the module diagram of Figure WU-1.

Fig. WU-1. Module diagram of K(wait-until).


This module is similar to the K(parallel merge) in that it is activated, waits until a Boolean input condition is satisfied, and then proceeds to activate the next module. Figure WU-2 shows the equivalent RTM macro formed from three conventional modules. For systems with an activate control signal identical to a Boolean, the K(wait-until) is identical to a K(parallel merge).


previous | contents | next