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The U.S. Department of Defense (DoD) supported the development of VHDL (VHSIC hardware description language) as part of the VHSIC (very high-speed IC) program in the early 1980s. The companies in the VHSIC program found they needed something more than schematic entry to describe large ASICs, and proposed the creation of a hardware description language. VHDL was then handed over to the Institute of Electrical and Electronics Engineers (IEEE) in order to develop and approve the IEEE Standard 1076-1987. 1 As part of its standardization process the DoD has specified the use of VHDL as the documentation, simulation, and verification medium for ASICs (MIL-STD-454). Partly for this reason VHDL has gained rapid acceptance, initially for description and documentation, and then for design entry, simulation, and synthesis as well.

The first revision of the 1076 standard was approved in 1993. References to the VHDL Language Reference Manual (LRM) in this chapter--[VHDL 87LRM2.1, 93LRM2.2] for example--point to the 1987 and 1993 versions of the LRM [IEEE, 1076-1987 and 1076-1993]. The prefixes 87 and 93 are omitted if the references are the same in both editions. Technically 1076-1987 (known as VHDL-87) is now obsolete and replaced by 1076-1993 (known as VHDL-93). Except for code that is marked 'VHDL-93 only' the examples in this chapter can be analyzed (the VHDL word for "compiled") and simulated using both VHDL-87 and VHDL-93 systems.

10.1  A Counter

10.2  A 4-bit Multiplier

10.3  Syntax and Semantics of VHDL

10.4  Identifiers and Literals

10.5  Entities and Architectures

10.6  Packages and Libraries

10.7  Interface Declarations

10.8  Type Declarations

10.9  Other Declarations

10.10  Sequential Statements

10.11  Operators

10.12  Arithmetic

10.13  Concurrent Statements

10.14  Execution

10.15  Configurations and Specifications

10.16  An Engine Controller

10.17  Summary

10.18  Problems

10.19  Bibliography

10.20  References

1. Some of the material in this chapter is reprinted with permission from IEEE Std 1076-1993, © 1993 IEEE. All rights reserved.

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