• Abstraction defines how much detail about the design is specified in a particular description.
• Four levels are:
– Layout level
– Logic level
– Register Transfer level
– Behavioral level
Layout Level
• This is the lowest level and describes the CMOS layout level design on silicon.
Logic Level
• Design has information about
– Function
– Architecture
– Technology
– Detailed timings
• Layout information and analog effects are ignored.
Register Transfer Level
• Using HDL every register in the design and the logic in between is defined.
• Design contains:
– Architecture information.
– No details of technology.
– No specification of absolute timing delays.
Behavioral Level
• Describing function of a design using HDL without specifying the architecture of registers
• Contains timing information required to represent a function
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