timescale

[Chris Carlen]

Hi:

I am using Xilinx Webpack and Modelsim XEII starter 5.7c to simulate
Verilog.

If I put a `timescale directive in my uut, the compiler complains
"module 'xxx' has a `timescale directive in effect, but previous modules
do not."

If I don't put in a `timescale directive, then it makes the same message
about the 'glbl' module.

Right now it gives peculiar results with the `timescale 10ns/1ns in my
source, but simulates correctly without the directive. Trouble is, it
has units of 1ps for each timestep without the directive.

How can I properly use the `timescale directive? This is only for
functional simulation to learn Verilog. I know that things will get
more complicated for synthesis for real devices.

Thanks for comments.

Good day!
--
____________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
crcarle@sandia.gov

 

[Chris Carlen]

Chris Carlen wrote:

Hi:

I am using Xilinx Webpack and Modelsim XEII starter 5.7c to simulate
Verilog.

If I put a `timescale directive in my uut, the compiler complains
"module 'xxx' has a `timescale directive in effect, but previous modules
do not."

If I don't put in a `timescale directive, then it makes the same message
about the 'glbl' module.

Right now it gives peculiar results with the `timescale 10ns/1ns in my
source, but simulates correctly without the directive. Trouble is, it
has units of 1ps for each timestep without the directive.

How can I properly use the `timescale directive? This is only for
functional simulation to learn Verilog. I know that things will get
more complicated for synthesis for real devices.

Thanks for comments.

Good day!

I made some progress by putting the `timescale directive in both the
source and test Verilog files. Then I just have to fiddle with the
options available in the Simulate and Simulate Options menus in Modelsim
to get the length of simulation and time axis resolution I want.

Good day!


--
____________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
crcarle@sandia.gov