Answers Database


NGDBUILD (EDIF2NGD): How does EDIF2NGD handle embedded ranged strings in array names?


Record #5416

Product Family: Software

Product Line: FPGA Implementation

Product Part: ngd2edif

Product Version: 1.5

Problem Title:
NGDBUILD (EDIF2NGD): How does EDIF2NGD handle embedded ranged strings in array names?


Problem Description:
Urgency: Standard

General Description: How does EDIF2NGD handle embedded ranged
strings in array names?


Solution 1:

EDIF2NGD 1.4 doesn't handle embedded ranged strings in array names
appropriately. The signal is recognized as 1-bit wide instead
of a vector.

When EDIF2NGD 1.5 expands an array construct, it *always* uses
parenthesis. The delimiters used in the range part of the
array name have no effect on the actual expansion.

EDIF2NGD 1.5 will attempt to match the array name to the following
array_name pattern:


array_name   := base_name range_suffix
base_name    := one or more valid characters for EDIF name
range_suffix := '[' boundA ':' boundB ']' |
		'<' boundA ':' boundB '>' |
		'(' boundA ':' boundB ')'
boundA	:= integer
boundB	:= integer

Consider these 3 EDIF snippets:

Ex 1:
(port (array (rename q_out "Q_OUT[9:0]") 10) (direction OUTPUT))

Ex 2:
(port (array (rename q_out "Q_OUT<9:0>") 10) (direction OUTPUT))

Ex 3:
(port (array (rename q_out "Q_OUT(9:0)") 10) (direction OUTPUT))

EDIF2NGD will handle array constructs with embedded ranges. Once the
bus index has been determined, the scalar port or net name will be
constructed as follows:

     base_name '(' index ')'

This bus-expansion syntax is one of the standard ones recognized by
NGDBUILD for Xilinx primitives that are defined to have bussed ports.
(Currently, only the Virtex block RAM primitives are so defined.) It is
also recognized by the Xilinx HDL writers when reconstructing bussed
ports on user entities.

After bus-expansion, all 3 of our examples will have the pattern,

base_name '(' index ')'

The original bus-notation will not be retained.

Note that in M2.1, many of these issues should go away, because
NGDBUILD will know how to juggle the delimiters to make pins
match.




End of Record #5416 - Last Modified: 01/18/99 19:21

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