VHDL Online books

http://esd.cs.ucr.edu/labs/tutorial/VHDL_Page.html
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VHDL Tutorial: Learn by Example
Basic Logic Gates
Combinational Logic Design
Typical Combinatinal Logic ComponentsLatch and Flip-Flops
Sequential Logic Design
Typical Sequential Logic Componentshttp://esd.cs.ucr.edu/labs/tutorial/