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Show 60 . of outputs from inputs is required only 1n the ease of scale of' two loops. The choice was made to use LATCH cells for all states since this maKes the mapping algorithm slightly easier. A more efficient version of the compiler should use LATCH2 for states not involved in scale-of-two loops. Each SICUDL external input variable maps to a single PPL inverter 'forward' transition. It detects the activation of the controlling (SICUINV) • GloDal inputs, which are usually boolean expressions of input variables, are compiled when they are first encountered in compiling a transition or generating a conditional output. The decision to compile inputs clos.e to the state in which they first appear and not to duplicate them is probably a good one since a given input will usually be locally used in most state-machines. Boolean expressions including an 'OH' require the construction of a temporary variable because ORing can only be done in PPL columns. Each transition which has outputs associated witn it will also require the construction of a temporary variable to indicate that the transition is currently being executed. Transitions are mappea to two PPL row segments. The firs is the state, detects tne deactivation of all possible predecessor states, activates the next states and controls any generated outputs. The second is the 'backward' transition. It detects the activation of the next state and deactivates the previous state. In the case of scaleof- two loops, tne bacxvar-c transition row segment also provides the mutual exclusion necessary by sensing that the input required for |
