15.4 Digital Logic Technologies 537
Today commonly the Silicon-on-insulator (SOI) technology is used to fabri-
cate integrated circuits. The SOI technology processes achieves a minimal
physical length below 100nm, advanced processes claim sizes below 20nm.
15.4 Digital Logic Technologies
The deployment of digital logic enables the optimized application-specific
design and implementation of various data processing architectures far
beyond traditional generic microprocessor system, though they are com-
monly implemented with large-scale digital logic, too. Digital logic itself is
inherently parallel. But a parallel system usually requires synchronization for
resolving competition (due to concurrent access of shared resources) and
providing coordination. The multiprocess model introduced in Chapter 5
offers such coordination and can be immediately transformed to digital logic
systems using Register-transfer architectures, briefly discussed in the next
subsection.
15.4.1 Register-Transfer Architecture
The Register-Transfer Level (RTL) architecture decomposes a traditional
program flow in a control and data flow. The control flow is represented by a
state diagram and implemented with a finite-state machine, consisting of a
control state register, a state transition logic, and an output logic. The data
flow is composed of registers storing intermediate or final results of expres-
sions, functional operators like arithmetic units performing the computation,
and finally data path flow selectors (multiplexer and demultiplexer), required
if resource sharing will be exploited, shown in Figure 15.9. The RTL architec-
ture is a base for different technological implementations discussed in the
next subsections.
The data path is controlled by a Finite State Machine (FSM), that activates
registers, selectors, and operational units depending on the current control
state. The control signals are generated in an output logic (). The next con-
trol state is computed by a state transition logic (), based on the current
control state stored in register Z and input from the data path, too.
The state machine itself is an RTL architecture, too, with only one register,
introducing some recursion of the architecture! The application-specific con-
trol and data path can be derived from a traditional program flow, discussed
in Chapter 12. The complexity of the RTL architecture depends strongly on the
complexity of the algorithms to be implemented. Resource sharing like regis-
ter merging in RAM blocks and state compaction can reduce the digital logic
resources significantly, but large control state diagrams beyond 1000-10000
states are not very well suited for this architecture, which should be imple-
mented preferred with program controlled machines (processors).
S. Bosse, Unified Distributed Sensor and Environmental Information Processing with Multi-Agent Systems
epubli, ISBN 9783746752228 (2018)