Real-Time Workshop

Introduction

External mode allows two separate systems -- a host and a target -- to communicate. The host is the computer where MATLAB and Simulink are executing. The target is the computer where the executable created by Real-Time Workshop runs.

The host (Simulink) transmits messages requesting the target to accept parameter changes or to upload signal data. The target responds by executing the request. External mode communication is based on a client/server architecture, in which Simulink is the client and the target is the server.

External mode lets you:

• Modify, or tune, block parameters in real time. In external mode, whenever you change parameters in the block diagram, Simulink automatically downloads them to the executing target program. This lets you tune your program's parameters without recompiling. In external mode, the Simulink model becomes a graphical front end to the target program.
• View and log block outputs in many types of blocks and subsystems. You can monitor and/or store signal data from the executing target program, without writing special interface code. You can define the conditions under which data is uploaded from target to host. For example, data uploading could be triggered by a selected signal crossing zero in a positive direction. Alternatively, you can manually trigger data uploading.

External mode works by establishing a communication channel between Simulink and code generated by Real-Time Workshop. This channel is implemented by a low-level transport layer that handles physical transmission of messages. Both Simulink and the generated model code are independent of this layer. The transport layer and the code directly interfacing to the transport layer are isolated in separate modules that format, transmit, and receive messages and data packets.

This design makes it possible for different targets to use different transport layers. For example, the GRT, GRT malloc, ERT, and Tornado targets support host/target communication via TCP/IP, whereas the xPC Target supports both RS232 (serial) and TCP/IP communication. The Real-Time Windows Target implements external mode communication via shared memory.

External Mode

Using the External Mode User Interface