AR# 424: XABEL 5.0 and XC7000 EPLDS: The .D extension is not supported by PLUSASM
AR# 424
XABEL 5.0 and XC7000 EPLDS: The .D extension is not supported by PLUSASM
描述
PROBLEM:
If the .D extension is used in XABEL and compiled to PLUSASM, it will be ignored and the resulting equations will reference the registered signal instead. PLUSASM does not have an analog to the .D extension and the XABEL compiler does not know how to handle it. The .D extension cannot be used on the left-hand side of an equation. (This is pointed out in the note at the bottom of page 7-11 of the XACT 5 X-Abel User Guide).
解决方案
WORKAROUND:
The same result may be accomplished by declaring a combinational signal signal_d to reference as the d input of the registered signal and then declaring a seperate registered signal with signal_q := signal_d.