Device-independent ABEL-HDL Sources

Most of the ABEL-HDL language is device-independent (for example, equations, truth tables, state machine descriptions and test vectors). However, the ABEL-HDL compiler needs some information describing how signals should function in logic descriptions. Some devices also have special functions that are accessed through conditionally-compiled syntax.

Information needed Provided in ABEL-HDL with

Output signal specifications Istype attributes in the signal declarations
and dot extensions on signals in the logic description.

Special functions Property Statements

Most common signal functions can still be described independent of a device with the pin-to-pin signal declarations. Some special features available in only certain classes of devices require device-specific signal declarations.

Pin-to-Pin Signal Specifications

Using ABEL-HDL's pin-to-pin syntax allows you to create logic descriptions that can be retargeted to different devices. We recommend you use the pin-to-pin syntax whenever you have a choice to allow the source to be retargeted with little modification.

Detailed Signal Specifications

Device-specific signal specification allows you to take advantage of unique features found only in certain device families.

Note: You can combine pin-to-pin and detailed signal declarations. In most cases, the ABEL-HDL compiler can reconcile the requirements of both types. In cases where the circuit function is ambiguous, the compiler displays an error message.

The ABEL-HDL syntax descriptions indicate whether the syntax is pin-to-pin or detailed.

ABEL-HDL Syntax