AR #18691 - 6.1i UNISIM, SIMPRIM, Simulation (ModelsSim) - Block RAM gives FATAL error when trying to load the simulation ("Fatal: (vsim-3421) Value -2147483648 is out of range 0 to 511")

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6.1i UNISIM, SIMPRIM, Simulation (ModelsSim) - Block RAM gives FATAL error when trying to load the simulation ("Fatal: (vsim-3421) Value -2147483648 is out of range 0 to 511")

AR#	18691
Part	SW-Sim Libraries
Last Modified	2008-11-19 00:00:00.0
Status	Archive
Keywords	RTL, simulation, UniSim, RAMB4, RAMB16, fatal, Verilog, VHDL, BRAM, index, out, range, 511, ModelSim, modelsim

Description

Keywords: RTL, simulation, UniSim, RAMB4, RAMB16, fatal, Verilog, VHDL, BRAM, index, out, range, 511, ModelSim, modelsim

Urgency: Standard

General Description:
When I try to load a simulation which has a BLOCK RAM in it, it gives the following FATAL error:

"Fatal: (vsim-3421) Value -2147483648 is out of range 0 to 511"

Why is this?

Solution

This happens anytime the address lines to the BLOCK RAM are not driven. When the address lines are not driven, they cause an 'X' on the input of the address lines and this creates the fatal error.

The problem can be worked around by ensuring that all address lines of the BRAM are driven.

In 6.2i, an error message will be displayed rather than this FATAL error, which tells the user to drive the ADDRESS lines with '1' or '0'.

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