Answers Database

XABEL,XACT-CPLD: Only one product term allowed for OE, Set, Reset, Clk (9500, 7300)


Record #1638

Product Family:  Software

Product Line:  EPLD Core

Problem Title:
XABEL,XACT-CPLD:  Only one product term allowed for OE, Set, Reset, Clk
(9500, 7300)



Problem Description:
The XC7300 and XC9500 devices only support a single product term
for output enables, register clocks, sets and resets.

In ABEL, any equation for nodes with the following dot extensions
may only have one product term.

.AP, .AR, .CLK, .OE, .PR, .RE

For example, the following equation will compile fine in ABEL,
but the XEPLD Fitter will issue an error.

DATA.OE = (A&B) # (C&D);

The error will read :
cl253: [Error] This type of equation can only have one product term.


Solution 1:

To fix the problem, declare a new node to implement the
equation with multiple pterms. Also declare the new node with
the ISTYPE 'KEEP' attribute to prevent the Abel Compiler from
collapsing the node and turning it back into a multiple
product term equation.

So, for the example given above, the new code would include:


DECLARATIONS

NEW	node istype 'keep';  "the new node

EQUATIONS

NEW = (A&B) # (C&D);  "assigning the multiple pterm equation
DATA.OE = NEW;	      "now the .OE equation is a single pterm



Solution 2:

In M1 (EDIF flow), you can use multiple p-term logic in all supported XABEL dot-
extension equations, including .clk, .oe, .ap, .ar, .pr, .re. The CPLD fitter au
tomatically creates nodes for the logic to feedback to the appropriate control p
-terms.



End of Record #1638