MATLAB DESIGN HDL CODER RELEASE NOTES User's Guide download pdf (Page 328)

328 www.xilinx.com System Generator for DSP User Guide

UG640 (v 12.2) July 23, 2010

Chapter 4: Importing HDL Modules

bidi_port.setGatewayFileName('bidi.dat');

end

In the above example, a text file "bidi.dat" is used during simulation to provide stimulation

to the port. The data file should be a text file, where each line represents the signal driven

on the port at each simulation cycle. For example, a 3-bit bi-directional port that is

simulated for 4 cycles might have the following data file:

ZZZ

110

011

XXX

Simulation will return with an error if the specified data file cannot be found.

Configuring Port Sample Rates

The black box block supports ports that have different sample rates. By default, the sample

rate of an output port is the sample rate inherited from the input port (or ports, if the inputs

run at the same sample rate). Sometimes it is necessary to explicitly specify the sample rate

of a port (e.g., if the output port rate is different than the block's input sample rate).

Note:

When the inputs to a black box have different sample rates, you must specify the sample rates

of every output port.

SysgenPortDescriptor provides a method, setRate, which allows you to explicitly set the

rate of a port.

Note:

The rate parameter passed to the setRate method is not necessarily the Simulink sample rate

of that the port runs at. Instead, it is a positive Integer value that defines the ratio between the desired

port sample period and the Simulink system clock period defined by the System Generator block

dialog box.

Assume you have a model in which the Simulink system period value for the model is

defined as 2 sec. Also assume, the example dout port is assigned a rate of 3 by invoking

the setRate method as follows:

dout.setRate(3);

A rate of 3 means that a new sample is generated on the dout port every 3 Simulink system

periods. Since the Simulink system period is 2 sec, this means the Simulink sample rate of

the port is 3 x 2 = 6 sec.

Note:

If your port is a non-sampled constant, you may define it as so in the configuration M-function

using the setConstant method of SysgenPortDescriptor. You can also define a constant by passing

Inf to the setRate method.

Dynamic Output Ports

A useful feature of the black box is its ability to support dynamic output port types and

rates. For example, it is often necessary to set an output port width based on the width of

an input port. SysgenPortDescriptor provides member variables that allow you to

determine the configuration of a port. You can set the type or rate of an output port by

examining these member variables on the block's input ports.

For example, you can obtain the width and rate of a port (in this case din) as follows:

input_width = this_block.port('din').width;

input_rate = this_block.port('din').rate;

Note: A black box's configuration M-function is invoked at several different times when a model is

compiled. The configuration function may be invoked before the data types and rates have been

propagated to the black box.

1 2 ... 323 324 325 326 327 328 329 330 331 332 333 ... 409 410

Comments to this Manuals

No comments

MATLAB DESIGN HDL CODER RELEASE NOTES User's Guide Page 328

Comments to this Manuals

Related products and manuals for Software MATLAB DESIGN HDL CODER RELEASE NOTES