The Simulink® Real-Time™ environment is a solution for prototyping and testing real-time systems using a desktop computer. In support of this, the software allows you to add I/O blocks to your model. The blocks of the Simulink Real-Time library provides a particular function of an I/O module. By using I/O blocks in your model, you can generate executable code tuned specifically to your I/O requirements.
You add I/O driver blocks to your Simulink model to connect your model to I/O modules (I/O boards). These I/O modules then connect to the sensors and actuators in the physical system.
Speedgoat real-time target machines are available with a number of I/O modules. See Speedgoat I/O Modules.
In addition to the blocks contained in the Simulink Real-Time library, you can also use third-party driver blocks in your Simulink Real-Time model. The description of these blocks is beyond the scope of the Simulink Real-Time documentation. See the provider of the third-party driver blocks for information on those boards and driver blocks.
A driver block does not represent an entire board, but an I/O section supported by a board. Therefore, the Simulink Real-Time library can have more than one block for each physical board. I/O driver blocks are written as C-code S-functions (noninlined S-functions). The source code for the C-code S-functions is included with the Simulink Real-Time software.
Note, if your model contains I/O blocks, take I/O latency values into account for the model sample time. To find latency values for a board supported by the Simulink Real-Time block library, consult the vendor data sheet. To find a link to the vendor web site, see:
To find latency values for Speedgoat boards, contact Speedgoat technical support.
The Simulink Real-Time system supports PCI and ISA buses. If the bus type is not indicated in the driver block number, you can determine the bus type of a driver block by checking the block's parameter dialog box. The last parameter is either a PCI slot, for PCI boards, or a base address, for ISA boards.
You can open the I/O device driver library with the MATLAB® command
slrtlib contains sublibraries grouped
by the type of I/O function they provide.
This library also contains the following blocks:
Simulink Real-Time Driver Examples — When you double-click this block, the Demos tab in the MATLAB Help Navigator opens, displaying the Simulink Real-Time examples and example groups.
Help for Simulink Real-Time — When you double-click this block, the Simulink Real-Time roadmap page is displayed. You can access the Simulink Real-Time documentation with this block.
Note: The Simulink Real-Time documentation describes only the Simulink Real-Time blocks. It does not describe the actual board. Refer to the board manufacturer documentation for information about the boards.
When you double-click one of I/O block groups, the sublibrary opens, displaying a list grouped by manufacturer. Double-clicking one of the manufacturer groups then displays the set of I/O device driver blocks for the specified I/O functionality (for example, A/D, D/A, Digital Inputs, Digital Outputs, and so on).
When you double-click one of the blocks, a Block Parameters dialog box opens, allowing you to enter system-specific parameters. Parameters typically include
Number of channels
PCI slot (PCI boards)
Base address (ISA/104 boards)
The Simulink Real-Time software reserves a 112 KB memory space for memory-mapped devices in the address range
C0000 - DBFFF
Drivers for some memory-mapped devices, such as the Softing CAN-AC2-104 board, support an address range higher than that supported by the Simulink Real-Time software. You must select an address range supported by both the device driver and the Simulink Real-Time software.
There are two types of ISA boards:
Jumper addressable ISA cards
PnP (Plug and Play) ISA cards
The Simulink Real-Time software only supports jumper addressable ISA cards (non-PnP ISA boards) where you have to set the base address manually.
The Simulink Real-Time I/O library supports I/O boards with a PCI bus. During the boot process, the BIOS creates a conflict-free configuration of base addresses and interrupt lines for the PCI devices in the target system. The user does not need to define base address information in the dialog boxes of the drivers.
PCI device driver blocks have an additional entry in their dialog
boxes. This entry is called
PCI Slot (-1 Autodetect) and
allows you to use several identical PCI boards within one target system.
This entry uses a default value of
-1, which allows
the driver to search the entire PCI bus to find the board. If you
specify a single number,
X, greater than
the driver uses the board in bus
When more than one board of the same type is found, you must use a
designated slot number and avoid the use of autodetection. For manually
setting the slot number you use a number greater than or equal to
0. If the board is not able to locate this slot in the target computer,
your real-time application will generate an error message after downloading.
If this additional entry is set to a value equal to or greater
0, you must be aware of the manufacturer's
identification number (Vendor ID) and the board identification number
(Device ID) of those boards supported by the I/O library. When the
target is booted, the BIOS is executed and the target computer monitor
shows parameters for the PCI boards installed on the target computer.
An example is shown below:
In this example, the third line indicates the location of the Measurement Computing™ PCI-DIO48
board. This is known since the Measurement Computing vendor ID
0x1307 and the device ID is
In this case, you can see that the Measurement Computing board
is plugged into PCI slot 11 (Device No.),
and that this value must be entered in the dialog box entry in your
I/O device driver for each model that uses this I/O device.
Properties for Simulink Real-Time I/O drivers are usually defined using the parameter dialog box associated with each Simulink block. However, for more advanced drivers, the available fields defined by text boxes, check boxes, and pull-down lists are inadequate to define the behavior of the driver. In such cases, you must provide a more textual description to indicate what the driver has to do at runtime. Textual in this context refers to a programming-language-like syntax and style.
The Simulink Real-Time software currently uses a character vector description contained in message structures for the conventional RS-232, GPIB, CAN (initialization), and the general counter drivers (AMD9513).
What is a message structure? — A message structure is a MATLAB array with each cell containing one complete message (command). A message consists of one or more statements.
|First Message||Second Message||Third Message|
Syntax of a message statement — Each statement in a message has the following format:
Structure_name(index).field_name = <field character vector or value>
The field names are defined by the driver, and need to be entered with upper- and lowercase letters as defined. However, you can choose your own structure name and enter that name into the driver parameter dialog box.
Creating a message structure — You could enter the message structure directly in the edit field of the driver parameter dialog box. But because the message structure is an array and very large, this becomes cumbersome very easily.
A better way is to define the message structure as a variable in the MATLAB workspace and pass the variable name to the driver. For example, to initialize an external A/D module and acquire a value during each sample interval, create a script file with the following statements:
Message(1).senddata='InitADConv, Channel %d' Message(1).inputports= Message(1).recdata='' Message(1).outputports= Message(2).senddata='Wait and Read converted Value' Message(2).inputports= Message(2).recdata='%f' Message(2).outputports=
This approach is different from other Simulink Real-Time driver blocks:
The script containing the definition of the message structure has to be executed before the model is opened.
After creating your Simulink model and message script, set the preload function of the Simulink model to load the script file the next time you open the model. In the Command Window, type
set_param(gcs, 'PreLoadFcn', 'script_name')
When you move or copy the model file to a new folder, you also need to move or copy the script defining the message structure.
During each sample interval, the driver block locates the structure defined in the Block Parameters dialog box, interprets the series of messages, and executes the command defined by each message.
Specific drivers and structures — For detailed information on the fields in a message structure, see the following topics:
You can save complete model simulation states while simulating, on a development computer, a Simulink model that contains some Simulink Real-Time blocks. The software does not support this behavior when executing such a model on the target computer.
For this operation, set the Save complete SimState in final state check box in the Data Import/Export pane of the Configuration Parameters dialog box. If your model contains the following blocks, you cannot save complete model simulation states while simulating on the development computer.
Async Buffer Read
Async Buffer Write
Baseboard Serial F
Bit Packing (Utilities library)
Bit Unpacking (Utilities library)
Byte Packing (Utilities library)
Byte Unpacking (Utilities library)
Commtech Fastcom® 422/2–PCI
Commtech Fastcom 422/2–PCI F
Commtech Fastcom 422/2–PCI-335
Commtech Fastcom 422/2–PCI-335 F
Commtech Fastcom 422/4–PCI-335
Commtech Fastcom 422/4–PCI-335 F
Condor® 1553 BC List
Create Ethernet Packet (Ethernet library)
Diamond Systems Emerald-MM Serial
Diamond Systems Emerald-MM Serial F
Diamond Systems Emerald-MM8 Serial
Diamond Systems Emerald-MM8 Serial F
FIFO bin read
FIFO ASCII read
Quatech DSCP-200/300 F
Quatech ESC-100 F
Quatech QSC-100 F
Quatech QSC-200/300 F
To prevent these messages, clear the Save complete SimState in final state check box in the Data Import/Export node of the Configuration Parameters dialog box.
In PWM and FM driver blocks, your control over the output frequency and duty cycle is not precise. In particular, these values are affected by the way that the base frequency is selected, as described in this section. The base frequency value is exact.
At the beginning of each sample time, two unsigned 16-bit integers,
are computed based on the block parameters and the current values
of the input signals. During the current sample period, the output
signal is held high for
m cycles of the base frequency,
low for the next
high for the next
m cycles, and so forth.
For a base frequency
b, this results in a
rectangular output signal of frequency
be integers, it is not possible to provide a continuous range of output
frequencies and duty cycles with perfect exactness.
For example, assume that you want to configure an FM block with
a duty cycle (
f to this block is a relative frequency.
It specifies an output frequency of
b × f.
n must be integers,
it is not always possible to find
n such that
b/n exactly and
2 × m (duty cycle
m/n = 1/2)
exactly. Such an exact match is only possible when the input signal
and so forth. The output frequencies for the intervening input signal
are approximate. The errors are smaller as
Hint, to achieve the smallest margin of error, select the largest
possible base frequency. The fact that
be 16-bit integers imposes a lower limit of
on the frequencies that can be generated using a given base frequency.
The typical Simulink Real-Time block documentation briefly describes the supported board, then describes the parameters for each of the blocks that support the board. Included in the documentation for each board is a board characteristics table. Board characteristics tables can include the following information:
|Board name||Name of the board supported by the blocks. For example, National Instruments® PCI-6221.|
|Manufacturer||Manufacturer of the board. For example, National Instruments.|
|Bus type||Bus that is used by the board. For example, PCI or ISA.|
|Access method||Whether the board is memory mapped or I/O mapped.|
|Multiple block instance support||If you can use multiple blocks for the same function on the same board. For example, different blocks for different channels of an A/D device.|
|Multiple board support||If you can use multiple boards of the same type in one real-time application.|