Answers Database

XABEL: How to assign preload value to registers in an EPLD


Record #1349

Product Family:  Software

Product Line:  Data I/O

Problem Title:
XABEL:  How to assign preload value to registers in an EPLD


Problem Description:
From my ABEL file, how can I control the preload value of macrocell registers
during device powerup?

*NOTE*:  This Solution applies to EPLDs only.  For information on assigning
preload values to FPGAs, see Solution #1350


Solution 1:

In M1, use:
  XILINX PROPERTY 'INIT=S|R signal_name...';

(xepld_property syntax is obsolete in M1.)



Solution 2:

To assign a preload value to a register, use the following
XEPLD property statement in the DECLARATIONS section of the
ABEL file.

xepld property 'EQUATION <reg_name>.PRLD = VCC|GND';


For example, to preload a register to 0 at powerup:

xepld property 'EQUATION <reg_name>.PRLD = GND';


OR, to preload a register to 1 at powerup:

xepld property 'EQUATION <reg_name>.PRLD = VCC';

Where <reg_name> is a register previously declared in the
DECLARATIONS section.



Solution 3:

In M1, use:
  xilinx_property 'init=s signal_name...';

(xepld_property syntax is obsolete in M1.)



End of Record #1349