Chapter 8. Resolved Signals

Throughout the previous chapters we have studiously avoided considering the case of multiple output ports connecting one signal. The problem that arises in such a case is determining the final value of the signal when multiple sources drive it. In this chapter we discuss resolved signals, the mechanism provided by VHDL for modeling such cases.

Basic Resolved Signals

If we consider a real digital system with two outputs driving one signal, we can fairly readily determine the resulting value based on some analog circuit theory. The signal is driven to some intermediate state, depending on the drive capacities of the conflicting drivers. This intermediate state may or may not represent a valid logic state. Usually we only ...

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