IEEE Std 1076.3-1997 IEEE Standard VHDL Synthesis Packages -Description

Abstract: The current interpretation of common logic values and the association of numeric values to specific VHDL array types is described. This standard provides semantic for the VHDL synthesis domain, and enables formal verification and simulation acceleration in the VHDL based design. The standard interpretations are provided for values of standard logic types defined by IEEE Std 1164-1993, and of the BIT and BOOLEAN types defined in IEEE Std 1076-1993. The numeric types SIGNED and UNSIGNED and their associated operators define integer and natural number arithmetic for arrays of common logic values. Two"s compliment and binary encoding techniques are used. The numeric semantic is conveyed by two VHDL packages. This standard also contains any allowable modifications.

Keywords: interpretations, metalogical values, numeric VHDL vector types, signed, synthesis, unsigned

Content

• 1. Overview
• • 1.1 Scope
  • 1.2 Terminology
  • 1.3 Conventions
• 2. References
• 3. Definitions
• 4. Interpretation of the standard logic types
• • 4.1 The STD_LOGIC_1164 values
  • 4.2 Static constant values
  • 4.3 Interpretation of logic values
  • • 4.3.1 Interpretation of the forcing and weak values (‘0’, ‘1’, ‘L’, ‘H’, FALSE, TRUE)
    • 4.3.2 Interpretation of the metalogical values (‘U’, ‘W’, ‘X’, ‘-’)
    • 4.3.3 Interpretation of the high-impedance value (‘Z’)
• 5. The STD_MATCH function
• 6. Signal edge detection
• 7. Standard arithmetic packages
• • 7.1 Allowable modifications
  • 7.2 Compatibility with IEEE Std 1076-1987
  • 7.3 The package texts
  • • 7.3.1 Package declaration for NUMERIC_BIT
    • 7.3.2 Package declaration for NUMERIC_STD
• Annex A Notes on the package functions
• • A.1 General considerations
  • • A.1.1 Mixing SIGNED and UNSIGNED operands
    • A.1.2 Mixing vector and element operands
  • A.2 Arithmetic operator functions
  • • A.2.1 Overflow of maximum negative value
    • A.2.2 Lack of carry and borrow
    • A.2.3 Return value for metelogical and high-impedance operands
  • A.3 Relational operator functions
  • • A.3.1 Justification of vector operands
    • A.3.2 Expansion of vector operands compared to integers
    • A.3.3 Return value for metalogical and high-impedance operands
  • A.4 Shift functions
  • • A.4.1 Multiplication by a power of 2 with remaindering
    • A.4.2 Division by a power of 2
  • A.5 Type conversion functions
  • • A.5.1 Overflow in conversion to INTEGER
    • A.5.2 Conversion between SIGNED and UNSIGNED
  • A.6 Logical operator functions
  • • A.6.1 Application to SIGNED and UNSlGNED
    • A.6.2 Index range of return values
  • A.7 The STD_MATCH function

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