AR# 939


Foundation Simulator - Macro outputs are always "Z" during simulation.


Keywords: Foundation, Simulator, Z, output

Urgency: Standard

Problem Description:
During simulation, the outputs of a user-created macro are always "Z" (schematic probes
are yellow).



(NOTE: The following resolution applies only to version 1.17 of the simulator, which was
shipped with Foundation 6.0.0.)

This can happen if the pin names on the macro symbol are written in lower-case. The
simulation netlist will convert all net names to upper-case, but leave the symbol names
in lower-case. The Foundation Logic Simulator is case-sensitive, so connectivity is lost
between the symbol pins and the underlying net names.

While loading the simulation netlist, the following messages will appear in the Project
Manager window:

SIM : Cannot find corresponding block pin for terminal A. Terminal will be
changed to label
SIM : No inputs in the node

Select the symbol and choose Options->Symbol Editor. Change the pin names to all
upper-case letters.


This can happen if the macro symbol pins are defined as passive.

- Select the symbol and choose Options->Symbol Editor. (The pin descriptions appear in the
lower left section of the Editor window.)
- If any pin is of type PAS, select the pin. The pin name, direction, and shape are listed above
the symbol graphic.
- Use the pull-down menus to change the pin type to IN, OUT, or HIZ (for 3-state outputs).


(The following applies to Foundation F1.x Simulator)

If the macro is generated from VHDL or ABEL code, the port name (pin name) has a length

1. Bus name <= 9 characters long
2. Signal name <= 14 characters long

When the VHDL code has port names that exceed this length, the pin name in the macro will
contain only 9 or 14 characters (i.e., busnametest: out STD_LOGIC_VECTOR (2 downto 0);
in macro symbol, the pin name changes to busnamete[2:0]).

Since the pin name changes in the macro, the connectivity will be lost between the pin name
and the underlying signal.

When loading simulation netlist, you will see the following message in the Project Manager

SIMUL: Cannot find corresponding block pin for terminal *
Terminal will be changed to label..

To solve this problem, limit the length of the pin names in VHDL/ABEL code as
specified above.


(The following applies only to Timing Simulations performed on back-annotated netlists for
3K devices):

NGD2EDIF, the utility which creates back-annotated netlists for timing simulation, may fail
to connect signals in the netlist. This may be confirmed by viewing the time_sim.edn file.

To correct this problem, change the following Simulation Settings under "Implementation

- Un-check "Correlate to Input Design."
- Un-check the "Preserve Hierarchy" option.

The new netlist should wire the signals correctly.
AR# 939
Date 08/12/2003
Status Archive
Type General Article
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