Expression typing

GUI expressions are typed. The supported types consist of six scalar types and two array types.

Scalar types

The scalar types are as follows: boolean, integer, real, time (64-bit integer), enumeration, and signal state. Signal states are represented by the nine VHDL std_logic states: 'U' 'X' '0' '1' 'Z' 'H' 'L' 'W' and '-'. Verilog states 0 1 x and z are mapped into these states and the verilog strengths are ignored. Conversion is done automatically when referencing Verilog nets or registers.

Array types

The array types supported are signed and unsigned arrays of signal states. This would correspond to the VHDL std_logic_array type. Verilog registers are automatically converted to these array types. The array type can be treated as either UNSIGNED or SIGNED, as in the IEEE std_logic_arith package. Normally, referencing a signal array causes it to be treated as UNSIGNED by the expression evaluator; to cause it to be treated as SIGNED, use casting as described below. Numeric operations supported on arrays are performed by the expression evaluator via ModelSim's built-in numeric_standard (and similar) package routines. The expression evaluator selects the appropriate numeric routine based on SIGNED or UNSIGNED properties of the array arguments and the result.

The enumeration types supported are any VHDL enumerated type. Enumeration literals may be used in the expression as long as some variable of that enumeration type is referenced in the expression. This is useful for sub-expressions of the form:

(/memory/state == reading) 

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