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AR# 5387

NGDBUILD: "logical block ' ' of type 'READBACK' is unexpanded" with a Exemplar netlist

Description

Keywords: Ngdbuild, rdclk, rdbk, readback, Exemplar, Galileo 4.2.2

Urgency: Standard

General Description:

Ngdbuild issues a warning on the instantiated READBACK component
in your HDL:

warning basnu:93-logical block 'rebk1' of type 'READBACK' is unexpanded.

Solution

Exemplar's Galileo 4.2.2 incorrectly declares the READBACK symbol in
the xc4000 libraries. The READBACK component is actually composed
of 2 components: 1 RDBK and 1 RDCLK. If these 2 components are
declared instead of READBACK, the design will be able to translate
through ngdbuild. The work around is:

Instantiate the RDBK and RDCLK components.

Please see (Xilinx Solution 3792) for HDL coding examples.

Note: Instantiating the RDCLK indicates to the FPGA that the USER
clock will be used for readback. If this is not the case, then only
instantion of the RDBK is necessary, and the FPGA will use the
onboard CCLK for readback.
AR# 5387
Date Created 01/12/1999
Last Updated 08/29/2001
Status Archive
Type General Article