PPT Slide
3 – Combinational Logic Implementation
Regular logic structures for multi-level combinational logic
Difficult to devise a regular structure for arbitrary connections between a large set of different types of gates
- efficiency/speed concerns for such a structure
- in 467 you'll learn about field programmable gate arrays (FPGAs) that are just such programmable multi-level structures
- programmable multiplexers for wiring
- lookup tables for logic functions (programming fills in the table)
- multi-purpose cells (utilization is the big issue)
Use multiple levels of PALs/PLAs/ROMs
- output intermediate result
- make it an input to be used in further logic